Sausage Gravy and Cheddar Biscuit Pot Pie

Name: Sausage Gravy and Cheddar Biscuit Pot Pie
Ingredients: 12 oz. pork breakfast sausage; ½ cups flour; 3½ cups milk; 1 cup heavy cream; 1 tbsp. apple cider vinegar; ¼ tsp. cayenne; Kosher salt and freshly ground black pepper, to taste; 3 cups flour, plus more for cutter; 3½ tsp. baking powder; 1½ tsp. kosher salt; 8 tbsp. unsalted butter, cubed and chilled, plus 2 tbsp. melted; 1½ cups buttermilk; 1½ cups shredded cheddar cheese; ¼ cups finely chopped chives, plus more for garnish; Hot sauce, for serving (optional)