In a skillet brown beef with union until full cooked. Drain off any grease.
Add mustard, ketchup, and brown sugar to the beef. Simmer for 5 minutes.
Spread butter over one side of each slice of bread.
For each sandwich, place one slice of bread, butter side down into a skillet.
Top with a little cheddar cheese, some of the beef mixture, and additional cheddar cheese.
Place an additional slice of bread on top, butter side up, creating the sandwich.
Cook over medium heat until both sides of the sandwich are toasted golden brown. Be careful when you flip it so the cheese and sloppy joe filling don’t fall out.
Repeat until all 5-6 sandwiches are made.