Baked Crepes With Ham and Mushrooms
Serves 4 to 6 3 eggs 1¾ cups milk ½ teaspoon kosher salt 1½ cups all-purpose flour 7 tablespoons unsalted butter, melted and cooled Clarified butter, melted, or canola oil, for brushing the pan For the filling 3 tablespoons unsalted butter, plus more for baking dish 1½ pounds button or cremini mushrooms, diced 1 teaspoon finely chopped fresh thyme Kosher salt and freshly ground black pepper 1½ tablespoons Dijon mustard 14 thin slices ham For the béchamel 2 tablespoons unsalted butter 2 tablespoons all purpose flour 1¼ cups milk. warm 5 ounces Gruyère cheese, grated 1 ounce Parmigiano-Reggiano, grated
To make the crepe batter: Put the eggs, milk and salt in the bowl of a blender and blend until smooth. Add the flour and blend for 20 seconds, then drizzle in the butter and blend for 10 seconds more. Let the batter stand for 20 minutes (the batter can be made a day ahead; cover tightly with plastic and refrigerate. Whisk well before using, as the flour will sink to the bottom of the bowl).
To make the filling: While the batter rests, make the filling. In a large frying pan over medium-high heat melt the butter. Add the mushrooms and a generous pinch of salt and cook, stirring. The mushrooms will at first be dry and squeaky in the pan, but as they cook they’ll release their liquid, which will evaporate. Cook until the mushrooms are tender and lightly browned, about 6 to 7 minutes. Remove from the heat, stir in the thyme and season to taste with additional salt and pepper. Set aside.
Heat an 8-inch crepe pan or nonstick frying pan over medium-high heat and brush with a small amount of clarified butter or oil. Lift the pan from the burner with one hand. With your other hand, ladle about a ¼ cup of batter into the center of the pan. Immediately tilt the pan in all directions so the batter spreads into a thin, even circle. Return the pan to the burner and cook until the edges of the crepe look papery and brown, about 20 to 30 seconds. With your fingers or an offset spatula, flip the crepe and cook on the second side until browned. Transfer to a plate. Repeat the process, greasing the pan with additional butter as necessary, until all the crepes have been cooked. You should have about 16 crepes, but often the first one you make may stick and the last one may be a bit small; the goal is 14 good crepes. The crepes can be stored tightly wrapped in the refrigerator for up to 3 days or frozen for up to a month. Before freezing, separate each crepe with a small piece of parchment or wax paper to prevent them from sticking.
Lightly butter a 9-inch-by-13-inch baking dish. Working with one crepe at a time, spread a very small skim coat of mustard on one side. Top with a slice of ham, followed by a spoonful of cooked mushrooms, arranging them in a line down the center. Tightly roll the crepe into a cylinder and place in the prepared baking dish. Repeat the filling and rolling until all of the crepes have been used.
To make the bechamel: In a medium saucepan, melt the butter. When the butter has melted, whisk in the flour and cook, whisking, until pale brown and toasty smelling, about 30 seconds. Whisk in the warm milk. Cook, whisking, until the mixture bubbles and thickens, then whisk in the Gruyère until melted and smooth. Season to taste with salt and pepper.
To serve: Spoon the bechamel over and around the crepes in the baking dish, and top with the grated Parmigiano. Arrange an oven rack 5 inches from the broiler and preheat the broiler. Slide the baking dish under the broiler, and broil until the bechamel is browned and bubbling, 3 to 4 minutes. Serve right away.