Beet and potato gratin with rosemary and walnuts

September 20, 2020 at 11:29 pm (B plus (3.5 stars, like a lot), Derek's faves, French, Monthly menu plan: dinner, Root vegetables, Winter recipes)

I first made this beet and potato gratin recipe back in 2010. I have since forgotten where the recipe originated. I’ve modified the recipe quite a bit in the intervening years. (The original recipe is at the end of this post if you want to see it.) Here is my current recipe. It has more cheese and less butter and cream than the original, and I’ve added walnuts and rosemary and omitted the breadcrumbs. The recipe is not really hard, but it is somewhat labor-intensive. I used to make it only about once a year, but as of 2023 I’m planning to make it maybe three or four times a year.

Ingredients

• 3 pounds beets, unpeeled
• 1.5 pounds potatoes, unpeeled
• 1 Tbs. butter (or however much you need to grease your pan)
• 1 cup / 4 oz. grated Parmesan cheese (or use another cheese like aged gouda)
• 1/2 cup / 2 oz. grated gruyere cheese (or use another firm cheese like comte or tete de moine)
• salt (Maybe 1 tsp. total? It probably depends on the exact amount of cheese used. I’ve actually never measured—I just sprinkle a little salt on each layer. But I’d like to get an amount down as it often comes out undersalted.)
• 1 tsp. pepper (ditto about the amount)
• 3 to 4 tsp. minced fresh rosemary
• 200g / 0.85 cups heavy cream
• lots of walnuts, pretty finely chopped (I think I use about 3/4 cup chopped walnuts maybe?)

Instructions:

1. Preheat the oven to 350 F.
2. Steam the beets and potato until tender when pierced with a knife. Note that even though the gratin cooks for another 30 to 40 minutes in the oven, you need the veggies to be tender before they go in the oven. For some reason they don’t really soften up at all in the oven. You can steam the veggies on the stovetop, but beets take a while, so I usually steam my veggies in my Instant Pot. I put the beets in first and cook them until they are about 3/4 done. (The exact time depends on their diameter–tables are online.) Then I add the potatoes and finish cooking both. Ideally you should do this well in advance so the veggies have time to cool and you aren’t trying to peel or slice boiling hot beets!
3. When the beets and potatoes are cool enough to handle, peel the beets. Depending on your potatoes you might want to peel them after they are cooked, but I usually don’t bother. I’ve never noticed the potato skins in the final dish. Cut both the beets and potatoes into 1/4-inch-thick slices, still keeping them separated.
4. Choose a gratin dish large enough to hold four layers of the sliced vegetables. (I use a 9×13 inch pyrex pan.) Grease the dish.
5. Build a gratin with 4 layers: beets, potatoes, beets, potatoes. After each vegetable layer sprinkle one quarter of the parmesan, gruyere cheese, salt, and pepper on top of the vegetable layer. After each layer sprinkle on 1/3 of the walnuts and rosemary. (I don’t put walnuts and rosemary on the top layer of potatoes because I’m afraid they will burn, but maybe it would work if you put them under the cheese?)
6. When all four layers are assembled, pour the cream evenly over the top.
7. Place in the oven and bake until the sauce is bubbling and the cheese on top is golden brown, 30 to 40 minutes.  Remove from the oven and serve hot or warm, scooping out portions with a spoon.

Update Feb 2023:

I cooked the beets in my instant pot, but they took forever. I think it was partly because the top layer wasn’t getting enough steam and then at some point after opening and closing it several times all the water had evaporated and I didn’t notice. I cooked the potatoes alone in the instant pot for 3 minutes plus quick release. The large potatoes were slightly overcooked for nice slicing but the golf-ball sized potatoes were mush. Next time I think I want to try just 2 minutes and use quite large potatoes.

Derek and Paul said the dish needed more potatoes. They suggested trying equal amounts of beets and potatoes, maybe around 2.25 pounds potatoes and 2.25 pounds beets? Derek put in much more than 1 Tbs. rosemary, but it didn’t taste too rosemary-y. I think the amount could easily be upped to 2 Tbs.

I like the very finely chopped walnuts on top, but inside the gratin it would be nice to have slightly larger pieces, maybe around the size of peanuts. Also I think 3/4 cup of walnuts is not enough. Maybe 1.5 cups would be better?

Derek thinks the dish needs much more cheese — at least twice as much. I like it even without a ton of cheese, but I’m sure it would be tasty with double the cheese.

I think 1/4 inch slices is too thick? I used the smallest slicing blade on my mandoline and they were much thinner than 1/4 inch thick.

I wonder if we should add some garlic as well?

Derek rated the gratin 3.5 stars out of 4, as did I. Alma (at 8 years old) rated it 3.25 stars out of 4.

To try next time:

Ingredients

• 2.25 pounds beets, unpeeled
• 2.25 pounds potatoes, unpeeled
• 1 Tbs. butter (or however much you need to grease your pan)
• 1.5 cups / 6 oz. grated Parmesan cheese (or use another cheese like aged gouda)
• 1 cup / 4 oz. grated gruyere cheese (or use another firm cheese like comte or tete de moine)
• salt (Maybe 1 tsp. total? It probably depends on the exact amount of cheese used. I’ve actually never measured—I just sprinkle a little salt on each layer. But I’d like to get an amount down as it often comes out undersalted.)
• 1 tsp. pepper (ditto about the amount)
• 2 Tbs. minced fresh rosemary
• 200g / 0.85 cups heavy cream
• 1.5 cups walnuts, chopped about pea-sized

Update Dec 2022:

I cooked the beets in my instant pot but just steamed the potatoes on the stovetop. I steamed them too long, however, because it was very hard to slice them without them falling apart. As a result I cut them too thick and didn’t love the texture in the final gratin. Is it really necessary to precook the potatoes? I wonder if I can just slice them very thinly and cook the gratin covered for a while? And maybe use pre-cooked and peeled beets? Then it could something I could make a bit more often?

Update Oct 11, 2021:

Alma has never liked this dish, but today she said it was “delectable” and ate thirds. I thought it came out really great as well. Derek said it was tasty but needed more cheese.

Notes from Sept 20, 2020:

I shattered my 9×9 inch pan a few months ago, so we used a 9×13 inch pyrex dish. It was bigger than necessary, but worked fine. I think next time maybe I’ll increase the amounts of veggies to make more gratin in the same pan. I forgot to measure my beets this time but I know I used almost 2 pounds of potatoes. I think maybe I used 5 medium/small beets (about 2.5 inches in diameter), so maybe only about 2 pounds?

I cooked the beets in the instant pot for 10 minutes under high pressure, left them for a bit, then did a quick pressure release and added the (medium-large) potatoes and cooked them for another 10 minutes under high pressure with a natural release. The beets came out perfectly–easy to peel but not mushy. But 10 minutes was too much time for the potatoes. They were way too soft. The skins were falling off and they were hard to slice. I couldn’t use the mandoline at all. They would have been great for mashed potatoes, but next time maybe I’ll try 15 minutes for the beets + QR and then only another 5 minutes extra once I add the potatoes.

This time we forgot to add walnuts but I definitely want to try adding them next time!

Definitely make sure your potatoes are on the top layer. They get nice and crispy, which doesn’t happen to the beets. And maybe reserve a bit more than 1/4 of the cheese for the topping?

I’ve made some version of this recipe a few times in the last couple of years, and Alma has never liked it. She will take a few bites of the cheesy top, but then rejects it. (She’s never liked non-crispy potatoes.) Tonight (at 5.5 years) she had a bit more than she has in the past, but we had challah on the table, so she mostly focused on that and wasn’t interested in the gratin.

My original notes from Nov 6, 2010:

Derek and I went to a local German restaurant a while back and I got a beet and potato gratin that had walnuts in it.  I really loved the beet and walnut combo, so I decided to try adding walnuts to this French recipe.  The recipe says to steam the beets and potatoes separately, then peel and slice them.  That was a huge pain.  I also don’t like peeling potatoes, as the skin is the best part. The steaming instructions confused me because they say to steam until tender but then you bake the gratin for another 30 minutes or so.  I was worried that the veggies would get overcooked, so I didn’t let them get totally tender.  That was a mistake, as the beets in the final dish were just a tad undercooked.  Once the veggies are steamed you slice them and then make a layer of beets, a layer of potatoes, and a final layer of beets.  Between the layers you sprinkle salt and pepper, rosemary, small amounts of parmesan and gruyere cheese, and dotted butter.  You then pour a mixture of cream and milk over the whole thing, and top it with bread crumbs and 1 Tbs. dotted butter.  But 1 Tbs. of butter is not enough to cover a 9×13 pan, and the bread crumbs ended up just like dry, sandy breadcrumbs.  Derek said he liked the topping though, despite its dry, sandy quality. He liked the dish a lot, actually.  He kept saying how flavorful it was, and tried to eat all the leftovers for breakfast.  My guests seemed to like it too, and even asked for the recipe.

I used less butter and added walnuts.  I used a light cream not heavy cream, and lowfat milk.  If I made this again I would double the rosemary and try it without pre-cooking the vegetables.  Steaming the beets and potatoes separately is a pain.  I might also try adding more cheese and skipping the cream altogether–just using milk.

And here’s the original recipe:

Ingredients

• 3 pounds beets, unpeeled
• 1.5 pounds potatoes, unpeeled
• 4 Tbs. butter
• 1/2 cup grated Parmesan cheese
• 1/4 cup grated gruyere cheese
• 1 tsp. salt
• 1 tsp. pepper
• 1 Tbs. minced fresh rosemary
• 1 cup heavy cream
• 3/4 cup milk
• 1/3 cup fine dried, bread crumbs, preferably homemade

Instructions:

1. Preheat the oven to 350 F.
2. Steam the beets until tender when pierced with a knife, 20 to 30 minutes.  Set aside.  Steam the potatoes separately in teh same way;  they should also be tender in 20 to 30 minutes.  (You can also boil instead of steaming.)  When the beets and potatoes are cool enough to handle, peel them and cut them into 1/4-inch-thick slices, still keeping them separated.
3. Select a gratin dish just large enough to hold three layers of the sliced vegetables.
   1. Layer 1:  Grease it with 1 Tbs. of the butter.  Arrange half of the beets in the bottom of the dish.  Sprinkle with one third each of the parmesan and gruyere cheese, salt, pepper, and rosemary.  Dot with 1 Tbs. of the butter.
   2. Layer 2:  Arrange all of the potatoes in a layer atop the beets.  Sprinkle with half of the remaining cheeses, salt, pepper, and rosemary.  Dot with 1 Tbs. of the butter.
   3. Layer 3:  Layer the remaining beet slices on top and sprinkle with the remaining cheese, salt, pepper and rosemary.
   4. Final topping:  In a vessel with a spout, combine the cream and milk and pour the mixture evenly over the top.  Strew the bread crumbs over the surface and dot with the remaining 1 Tbs. butter.
4. Place in the oven and bake until the sauce is bubbling and the topping is golden brown, 30 to 40 minutes.  Remove from the oven and serve hot or warm, scooping out portions with a spoon.