Baked Crepes with Creamy Mushrooms and Prosciutto

Ingredients

• 1/2 ounce dried wild mushrooms
• 6 tablespoons unsalted butter
• 1 medium yellow onion, minced
• 1/2 pound fresh button mushrooms, thinly sliced
• 6 ounces thinly sliced prosciutto, cut into thin strips
• 2 tablespoons all-purpose flour
• 2 cups milk
• 3/4 cup grated Parmigiano Reggiano