Adjust oven rack to upper position, and set oven to broil. You may also use a toaster oven to cook the sandwiches if you don't want to broil them in the oven. Place bacon in a large, deep skillet. Cook over medium high heat until evenly brown and crispy. Drain on paper towels. Place a few spears of asparagus on a slice of bread. Top with 2 slices crisp bacon then a slice of cheese. Toast under the broiler until the cheese is melted and bubbly.