Week 21: Sweet Potato and Swiss Chard Gratin

It’s time for cheesy comfort food, my friends. It’s getting below 10 degrees at night and we had our first frosty grasses yesterday morning! So exciting. This recipe is a great way to cram as many wilted greens as possible into a freezer and lunch friendly recipe that will keep you warm and toasty through and through.

This is a Smitten Kitchen recipe, one of our go-to inspiration blogs. It is a medium to-do as soon as you get into making a roux and layering ingredients. But the whole thing did go together in under 20 minutes, and then baked for an hour as we waited impatiently. Because oh my goodness, this thing smells amazing. The thyme, sweet potato, and cheese combo is a natural.

Two things I would change for next time are: 1. squeeze the heck out of those greens – I did a middling job of this and it meant the resulting gratin is just a bit soggier than I would prefer. The original author stresses this and I really should have taken her more seriously. And 2., I would maybe try to add a bit of white wine to the béchamel before pouring it over the cheese and veg. I just feel like it wouldn’t hurt to have a bit of acid and it might bring out the thyme flavour a bit more. Otherwise, 10/10, will eat again!

Sweet Potato and Greens Gratin


  • 1/4 cup butter
  • 1 small onion finely chopped
  • 3 pounds Swiss chard leaves and stems separated and both cut into 1-inch pieces (we used a mixture of Swiss Chard, kale, and arugula)
  • Pinch of freshly grated nutmeg
  • 2 cups heavy cream or whole milk
  • 2 garlic cloves minced
  • 2 tablespoons flour
  • 2 pounds medium red-skinned sweet potatoes, peeled and cut into 1/8-inch thick rounds (we didn't peel them – just scrubbed)
  • 1 tablespoon minced fresh Italian parsley
  • 1 tablespoon minced fresh thyme
  • Fine sea salt
  • Freshly ground black pepper
  • 1 1/4 cups about 5 ounces coarsely grated Gruyére cheese (we used a mix of mozzarella and parmesan)


  1. Prep greens: Cook onion in 2 tablespoons butter in a wide 8-quart heavy pot over moderately low heat, stirring, until softened. Add chard stems, pinch of nutmeg, and salt and pepper to taste and cook, stirring, until vegetables are tender but not browned, about 8 minutes. Increase heat to moderately high and add chard leaves by large handfuls, stirring, until all greens are wilted. Season with salt and pepper then transfer greens to a colander to drain well and press out liquid with back of a large spoon.
  2. Make sauce: Combine cream or milk and garlic in small saucepan; bring to simmer; keep warm. Melt two tablespoons butter in a medium heavy saucepan over moderate heat and stir in flour. Cook roux, whisking, one minute, then slowly whisk in warm cream/milk and boil, whisking, one minute. Season sauce with salt and pepper.
  3. Assemble gratin: Preheat oven to 400°F. Butter deep 9×13 baking dish. Spread half of sweet potatoes in the prepared baking dish. Sprinkle with salt, pepper, a quarter of the herbs and a 1/4 cup of the cheese. Distribute half of the greens mixture over the cheese, then sprinkle salt, pepper, a quarter of the herbs and 1/4 cup of the cheese over it. Pour half of bechamel sauce over the first two layers then continue with the remaining sweet potatoes, more salt, pepper, herbs and cheese and then the remaining greens, salt, pepper and herbs. Pour the remaining sauce over the top of the gratin, pressing the vegetables slightly to ensure that they are as submerged as possible. Sprinkle with the last 1/4 cup of cheese.
  4. Bake gratin for about 1 hour until golden and bubbly, and most of the liquid is absorbed. Let stand 10 minutes before serving.