Invert a large muffin pan, and place bacon slices around the outside of 4 individual muffin cups. Secure ends of bacon with wooden picks.
Place inverted muffin pan with bacon on upper shelf of oven. Bake at 350° for 15 minutes or until bacon is crisp. Remove from oven, and carefully remove bacon rings from muffin cups. Remove wooden picks.
Gently slide 5 to 6 cooked asparagus spears inside each bacon ring. Pour a small amount of melted butter over each serving, and season with salt and pepper. Serve immediately.