Mushroom and Leek Quiche with Gruyere

Ingredients (11)

• 1 deep dish 9 inch pie crust
• 3 Tablespoons butter, divided
• 3 leeks, white and light green parts only
• 12 ounces sliced mushrooms
• 8 eggs
• 1 cup whole milk
• 1 cup heavy cream
• 1 teaspoon salt
• 1/4 cup flour (optional)
• 2 cups shredded gruyere cheese, divided
• 1/4 cup Parmesan cheese