Special equipment: a 12-cup nonstick muffin tin
For the eggs Benedict: Preheat the oven to 350 degrees F. Spray a 12-cup nonstick muffin tin very generously with nonstick spray.
Cut each biscuit in half horizontally and press out into a 4- to 5-inch circle. Firmly press the circles into the bottom and up the sides the muffin cups.
Divide the bacon among the muffin cups. Top each cup with an egg, and sprinkle with salt and pepper. Bake until the eggs are just set, 15 to 20 minutes.
For the Hollandaise: Put the egg yolks, vinegar and cayenne in a blender. Pulse a few times to combine.
Put the butter in a microwave-safe bowl or liquid measuring cup and microwave until just melted.
With the blender running, gradually add the melted butter to make a smooth sauce. If the sauce seems too thick, add about 1 teaspoon warm water to loosen it. Season with salt.
To serve: Run a thin knife around the edge of each muffin cup and gently pop out the eggs Benedict onto a cutting board. Serve immediately, topped with the Hollandaise and sprinkled with scallions.