BAKE THE BACON: Preheat the oven to 425°. Arrange the bacon on a rack set over a baking sheet. Cook until golden and crisp, about 30 minutes.
MAKE THE GRAVY: In a saucepot set over medium heat, melt the butter. Add the onions and garlic, and saute until translucent, about 5 minutes; stir in the flour and cook, stirring continuously, until roux is a rich caramel color and smells nutty, about 5 more minutes. Add the stock, coffee, paprika, black pepper and cayenne and cook, stirring occasionally, until thickened, about 15 minutes; stir in the cream and season to taste with salt.
MAKE THE CHEESE SAUCE: In a small saucepan, bring the milk to a simmer. In a medium saucepan, melt the butter. Add the flour and whisk over medium heat for 1 minute. Gradually whisk in the hot milk and bring to a boil. Cook, whisking, until thickened, about 5 minutes. Remove the pan from the heat and whisk in the sharp white cheddar and Parmigiano-Reggiano until melted. Stir in the hot sauce and season with salt and pepper.
BUILD THE SANDWICHES: Top each biscuit with some turkey, cheese sauce, gravy and bacon.