In a large skillet over medium heat, add the ground beef. Use a wooden spoon to break it up into smaller pieces as it cooks. Cook until browned, about 5-7 minutes. This step is crucial as browning the meat enhances the flavor.

Once the beef is browned, drain any excess fat from the skillet. This helps prevent the filling from being greasy.

Add the diced onion and green bell pepper to the skillet. Sauté for about 3-4 minutes until the vegetables are softened. This adds texture and flavor to the filling.

Stir in the minced garlic and cook for an additional 1 minute until fragrant. Garlic adds a wonderful aroma and depth to the dish.

Reduce the heat to low and add the ketchup, Worcestershire sauce, brown sugar, mustard, smoked paprika, salt, and black pepper. Stir well to combine all ingredients.

Simmer the mixture on low heat for about 10 minutes, stirring occasionally. This allows the flavors to meld together, creating a rich and savory sauce.

While the filling simmers, lightly toast the hamburger buns if desired. This adds a nice crunch and prevents the buns from becoming soggy.

Once the filling is ready, spoon a generous amount onto the bottom half of each bun. The filling should be heaping to ensure every bite is flavorful.

Top with the other half of the bun and serve immediately. Enjoy your Manwich Sloppy Joes with a side of fries or a salad!