For the biscuits: Preheat the oven to 450 degrees F.
Whisk together the flour, powdered milk, baking powder, sugar, cream of tartar, salt and cayenne pepper in a medium bowl. Using a pastry cutter, cut the butter bits and shortening into the dry mixture until blended thoroughly. Mix in the cheese, then fold in the buttermilk until the dough comes together.
On a lightly floured surface, turn out the dough and press into a circle 1 to 1 1/2 inches thick. Cut out circles with a biscuit cutter or a glass. Place the biscuits in cast-iron skillets, then brush the tops with the melted butter. Bake until golden brown, 10 to 12 minutes, then set aside to cool a little.
For the sandwiches: Next, add the sausage patties to a skillet over medium heat and fry until cooked through. Set aside and keep warm. In the same skillet, fry the eggs, turning them over to cook the yolks through.
Now make a sandwich by cutting a biscuit in half. Put a sausage patty on the bottom half. Top with an egg, some hot sauce and a slice of cheese. Cover with the top and eat, or wrap in foil to keep warm.