1. Heat the oven to 425°F. Press the wonton wrappers into 24 (1 1/2-inch) mini muffin-pan cups.
2. Cook the beef in a 10-inch skillet over medium-high heat until well browned, stirring often to separate meat. Pour off any fat. Stir in the taco seasoning mix and 1/4 cup salsa.
3. Spoon the beef mixture into the wonton cups. Top with the remaining salsa and the cheese.
4. Bake for 5 minutes or until the wontons are golden brown and the cheese is melted. Top with the sour cream, if desired.