- 1 1/2 pounds lean ground beef
 - 3/4 cup crumbled blue cheese
 - 1/2 cup diced onion
 - 1/2 cup Italian bread crumbs
 - 1/2 cup chopped fresh spinach
 - 2 eggs
 - 2 tablespoons Worcestershire sauce
 
- Preheat an oven to 375 degrees F (190 degrees C). Grease a large muffin pan with cooking spray.
 - Combine ground beef, blue cheese, onion, bread crumbs, spinach, eggs, and Worcestershire sauce in a large bowl until well blended. Divide meat mixture evenly into the prepared muffin pan.
 - Bake in the preheated oven until no longer pink in the center, about 30 minutes. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).