Hands on time: 20 minutes Total time: 50 minutes Serves: 8
3 tablespoons unsalted butter, room temperature, divided 2 cups whole milk 3 sprigs flat-leaf parsley 2 sprigs thyme 10 whole black peppercorns 2 tablespoons canola oil 1 bunch green onions, white and green parts, sliced 4 medium yellow squash, quartered and cut into 1/2-inch-thick slices 4 medium zucchini, quartered and cut into 1/2-inch thick slices Coarse salt and freshly ground black pepper 1 clove garlic, very finely chopped 1 teaspoon freshly chopped thyme leaves 2 tablespoons all-purpose flour 1 to 1 1/4 cups freshly grated Gruyere, Emmenthaler or Swiss cheese 3 large eggs, lightly beaten Pinch cayenne pepper 1 cup panko (Japanese bread crumbs) or fresh bread crumbs 1/4 cup freshly grated Parmigiano-Reggiano
Preheat oven to 350 degrees. Brush a medium baking dish with 1 tablespoon of the butter. Set aside. Heat the milk in a medium saucepan over medium heat. Add the parsley, thyme and peppercorns. Cover and set aside to steep. Heat the oil in a large skillet over high heat. Add the green onions and squash and zucchini; season with salt and pepper, and cook until tender, about 8 minutes. Add the garlic and thyme, and cook until fragrant, 30 to 45 seconds. Place the mixture in a colander to drain. Reduce heat to medium. Melt the remaining 2 tablespoons butter in the same skillet used to cook the squash. Add the flour, and stir until foamy. Strain the heated milk into the butter-flour combination, and stir to combine. Bring to a boil, and cook until the sauce is thick enough to coat the back of a spoon, about 3 minutes. Blend in the cheese. Blend a little bit of the sauce into the beaten eggs. Then add the egg mixture back to the sauce. Add a pinch of cayenne and season to taste with salt and pepper. Combine the panko and Parmigiano-Reggiano in a small bowl. Set aside. Add the well-drained squash mixture to the sauce and stir to combine. Transfer the mixture to the prepared baking dish. Top with the panko-cheese mixture. Transfer to oven, and bake until bubbly and set, about 30 minutes. If necessary, for the last few minutes, broil until the topping is a rich golden brown, 2 to 3 minutes.
A gratin is any dish that is topped with cheese or cheese and bread crumbs, then heated in the oven until brown and crispy. Sounds fancier than casserole, doesn't it? Gruyere and Parmigiano-Reggiano are two cheeses often used in preparing a gratin. Both are low-moisture cow's milk cheeses with sweet, rich, almost nutty flavors. If you wanted to stay truer to Southern roots, cheddar cheese may be substituted for the Gruyere in the sauce.