Cheesy Beef Melt Sandwich

In a large skillet, brown ground beef and onion over medium-high heat until fully cooked. Drain off any excess grease.

Add mustard, ketchup, and brown sugar to the cooked beef mixture, stirring until well combined. Reduce the heat, and let it simmer for 5 minutes or until slightly thickened.

Preheat a large non-stick skillet or griddle over medium heat.

Spread a thin layer of softened butter on one side of each white bread slice.

Place one slice of bread, butter side down, on the preheated skillet. Top with a 1/4 cup of shredded sharp cheddar cheese, followed by 1/5 of the beef mixture, and another 1/4 cup of shredded cheese. Place another slice of bread on top, butter side facing up.

Cook each sandwich for about 3 to 4 minutes per side, until the bread is golden brown and cheese is melted. Gently press down on the sandwich with a spatula while cooking, and carefully flip the sandwich to cook the other side.

Repeat the process to make a total of 5 sandwiches, and serve immediately.