Biscuits and Gravy Casserole - Master recipes

Ingredients

• For the biscuits: -
• 2 1/4 cups (315 g) all-purpose flour (see Recipe Note) -
• 3 tablespoons cornstarch -
• 1 tablespoon baking powder -
• 3/4 teaspoon kosher salt -
• 1/2 cup unsalted butter, cold -
• 1 cup buttermilk, cold -
• For the gravy: -
• 1 tablespoon olive oil -
• 1/2 pound sliced mushrooms -
• 1/4 cup chopped yellow onions -
• 1 pound breakfast pork sausage -
• 6 tablespoons all-purpose flour -
• 1/2 teaspoon ground sage -
• 1/2 teaspoon freshly ground black pepper -
• 1/8 teaspoon ground nutmeg -
• 2 1/2 cups milk, preferably whole -
• For topping: -
• 1 tablespoon unsalted butter, melted -