6 pounds Swiss chard
2 cloves garlic, peeled and chopped
1/4 cup minced onion
1 tablespoon olive oil
3 tablespoons butter
3 tablespoons flour
2 1/2 cups warm milk
3 teaspoons Daniel Boulud's Thanksgiving Spice Blend
1/2 cup shredded Gruyère cheese
1/3 cup grated Parmesan cheese
Salt and pepper to taste
Preheat oven to 375 degrees F.
Bring a large pot of salted water to a boil and place a bowl of ice water on the side. Separate the Swiss chard leaves from the stems, and reserve half of the stems; rinse well. Boil the Swiss chard leaves until tender; remove with a slotted spoon and chill in the ice water. Strain well by wrapping in cheesecloth or a clean dish towel and wringing out the liquid; then chop roughly. Cut the reserved Swiss chard stems into thin slices.
In a large saucepan over medium-low heat, add the olive oil, garlic, onion, sliced Swiss chard stems and one teaspoon of Thanksgiving Spice Blend and cook, stirring until tender. Stir in the cooked Swiss chard leaves to combine.
In a separate small pot over medium-low heat, add the butter, flour and 1 teaspoon of Thanksgiving Spice Blend. Cook, stirring with a whisk for 2-3 minutes, being careful not to brown the butter. Gradually whisk in the warm milk. Continue to cook, whisking, for 3 minutes to make a bechamel sauce. Transfer the bechamel into the pot with the Swiss chard, and stir to combine; season with salt and pepper to taste.
Transfer to a small gratin dish or ovenproof baking pan. Sprinkle evenly with the grated Parmesan and Gruyere cheeses, and the remaining teaspoon of Thanksgiving spice blend and bake 8-10 minutes, or until golden brown.