Step 1: Brown the Beef and Onions

In a large skillet, cook the ground beef over medium heat until browned and fully cooked. Use a spoon or spatula to break the meat into crumbles. Add the diced onions to the skillet and sauté for about 3-4 minutes, or until the onions soften. Drain off any excess grease.

Step 2: Add the Sauce Ingredients

Reduce the heat to low. Stir in the ketchup, brown sugar, and mustard. Mix well until everything is fully combined.

Step 3: Simmer the Mixture

Let the beef mixture simmer on low for 10-15 minutes, stirring occasionally. This allows the flavors to meld together, and the sauce will thicken slightly.

Step 4: Taste and Adjust Seasoning

Taste the mixture and add salt and pepper as needed. If you prefer a little tangier flavor, add an extra teaspoon of mustard. For a touch more sweetness, stir in a bit more brown sugar.

Step 5: Assemble the Sloppy Joes

Spoon the hot meat mixture onto buns or sandwich rolls. Serve immediately for the best flavor and texture.