Ingredients:
1 lbs Swiss chard
2 lbs medium sweet potatoes, peeled
2 tbsp of butter
1 small onion, finely chopped
pinch of freshly grated nutmeg
salt and pepper to taste
1 tbsp fresh parsley, minced
1 tbsp fresh thyme, minced
1 1/4 cups (about 5 ounces) Gruyere cheese, coarsely grated
2 cups heavy cream or whole milk
2 garlic cloves, minced
2 tbsp of butter
2 tbsp flour
Directions:
Preheat oven to 400°. Separate Swiss chard leaves and stems, and chop both into 1/2 inch pieces. Slice the peeled sweet potatoes into rounds about 1/8 inch thick.
Begin by sautéing chard stems in a small amount of oil, adding the leaves after about 5 minutes. Season with salt to help draw the moisture out of the greens. Stir often, until all parts are tender but not browned, about 8 minutes. Transfer to colander and press with a spatula or spoon to express excess water from the chard. It is important to remove as much liquid as possible!
Heat 2 Tablespoons of the butter in a large, heavy pot over medium-low heat, and cook the onion, stirring, until softened. Season with nutmeg, salt and pepper. Assemble the roux by adding 2 Tablespoons flour to this mixture, and cook for about 1 minute. Slowly whisk in warm milk or cream, adding more as the mixture begins to thicken. Bring the sauce to a gentle simmer, whisking constantly, and cook about one minute, then remove from heat. Separate 1.5 cups of the béchamel for layering and mix the drained Swiss chard mixture into the remaining sauce.
Butter a 9” x 13” baking dish. Spread the chard and béchamel mixture in the bottom of the pan. Sprinkle with salt, pepper, the herbs and 1/4 of the cheese. Then layer the thinly sliced sweet potatoes, alternating with the remaining béchamel, cheese and herbs until all are used.
Bake the gratin for about 1 hour until golden and bubbly, and most of the liquid has been absorbed. Let stand for 15 minutes before serving.
Adapted from smittenkitchen.com