In a skillet, cook beef and onion over medium heat until meat is no longer pink; drain.

In a bowl, combine the flour, sugar, baking powder and salt.

In another bowl, combine the ketchup, milk, butter, eggs, and mustard. Stir into the dry ingredients just until moistened.

Fold in the beef mixture and cheese.

Fill greased miniature muffin cups three-fourths full.

Bake at 425°F for 15-18 minutes or until a toothpick comes out clean.

Cool for 5 minutes before removing from pans to wire racks.

Refrigerate leftovers, or freeze.

YIELD: 5 dozen

NOTE: Muffins may be baked in regular-size muffin cups for 20-25 minutes; recipe then makes 2 dozen.