Ingredients

FOR THE MORNAY SAUCE: 2 tablespoons butter 1/4 cup finely chopped onion Pinch of kosher salt 1 bay leaf 2 tablespoons all-purpose flour 2 cups whole milk 1/2 cup finely grated Gruyere cheese 1/4 cup finely grated Parmigiano-Reggiano 1 large egg yolk FOR THE SANDWICHES: 6 tablespoons unsalted butter 8 slices fresh country-style white bread 1 pound Gruyere cheese, sliced 1/16 inch thick (about 24 slices) 12 ounces thinly sliced ham (about 16 slices)

Description

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