Ingredients
Equipment
Method
- Step 1: Preheat your oven to 180°C (Thermostat 6).
- Step 2: In a large skillet, pour a good drizzle of olive oil and heat over medium heat. Add the thinly sliced red onion and let it sweat until tender and translucent (a few minutes). Then, add the minced garlic and cook for another minute.
- Step 3: Add the fresh spinach to the skillet. It will make a mountain at first, but don't worry, it will reduce quickly. Cook just until it wilts and becomes tender. Season with salt and pepper to your taste. Remove the skillet from the heat and set this flavorful mixture aside.
- Step 4: Take a medium-sized gratin dish (which can hold about 6 to 8 portions). Lightly oil it so nothing sticks.
- Step 5: Layer the gratin. Arrange a first layer of thin sweet potato slices on the bottom of the dish. Then, cover with a portion of the spinach-onion-garlic mixture you prepared. Scatter a generous amount of crumbled feta over it. Repeat these layers: sweet potatoes, spinach mixture, feta... until you run out of ingredients. Finish with a layer of feta cheese so the top gratins nicely.
- Step 6: Gently pour the heavy cream over the entire surface of the gratin, trying to distribute it evenly so it seeps between the layers.
- Step 7: Bake! (First phase): Cover the dish with aluminum foil. This allows the sweet potatoes to cook through without the top burning. Bake for 40 minutes.
- Step 8: Bake! (Second phase): After 40 minutes, gently remove the aluminum foil. Continue baking for about 10 additional minutes, or until the top is nicely golden and gratinéed as you like it.
- Step 9: Let it rest: This is the crucial step many forget! Take the gratin out of the oven and let it rest quietly for 5 to 10 minutes before serving. This allows the flavors to stabilize and the gratin to hold together better when cut. And, it prevents you from burning your tongue!
Notes
Substitutions & Additions: Swap sweet potatoes with squash (butternut, pumpkin) or a mix of sweet and classic potatoes. Kale or chard can replace spinach. Replace feta with crumbled goat cheese, ricotta, or grated mozzarella (add to the top layer). Add chopped nuts, pumpkin or sunflower seeds for crunch. Enhance flavor with a pinch of grated nutmeg in the cream, herbs de Provence, or a hint of chili. For non-vegetarians, add cooked smoked lardons or chicken pieces with the spinach mixture.
Tips for Success: Slice sweet potatoes thinly for even cooking (a mandoline helps, but be careful!). Don't overcook spinach in the pan; just wilt it. Taste and season the spinach mixture, remembering feta is salty. Don't skip the resting step! It's crucial for texture. You can prep the spinach mixture and slice potatoes ahead of time. The assembled gratin can also wait in the fridge, but may need 5-10 min extra initial cooking under foil.
Storage: If leftovers remain, store in an airtight container once completely cooled. Keeps 2-3 days in the fridge (reheat gently). Can be frozen, but texture may change slightly upon thawing; thaw in fridge and reheat in oven.
FAQ: Can I use frozen spinach? Yes, but thaw and squeeze out as much water as possible to avoid a watery gratin. Can I replace sweet potato with potato? Yes, the taste will be different (less sweet) but it works well. You can also mix both. I don't like feta, what can I replace it with? Use crumbled fresh goat cheese, mozzarella, or a grated cheese blend. For vegan, try nutritional yeast for a cheesy flavor.