1Heat oven to 375°F. Spray 12 regular-size muffin cups with cooking spray.
2In 10-inch skillet, cook beef and onion over medium-high heat 5 to 7 minutes, stirring frequently, until beef is thoroughly cooked; drain. Cool 5 minutes; stir in blue cheese and Worcestershire sauce.
3In medium bowl, stir baking mixture ingredients with whisk or fork until blended. Spoon 1 scant tablespoon baking mixture into each muffin cup. Top with about 1/4 cup burger mixture. Spoon 1 tablespoon baking mixture onto burger mixture in each muffin cup.
4Bake 25 to 30 minutes or until toothpick inserted in center comes out clean and tops are golden brown. Ten minutes into baking, carefully open oven and sprinkle 1/2 tablespoon French-fried onions on top of each muffin. Close oven door and finish baking. Cool 5 minutes. With thin knife, loosen sides of pies from pan; remove from pan and place top sides up on cooling rack. Cool 10 minutes longer, and serve.