Make the Sloppy Joe Filling:
In a large skillet over medium-high heat, cook the ground beef for about 5–6 minutes, breaking it up into small pieces as it browns. Drain excess fat if needed.
Sauté Veggies:
Add the diced onion, bell pepper, and garlic. Cook for an additional 2–3 minutes until softened and fragrant.
Simmer the Sauce:
Stir in ketchup, tomato paste, Worcestershire sauce, mustard, chili powder (if using), salt, pepper, and water. Mix thoroughly and reduce heat to low. Simmer for 5–7 minutes until thickened. Set aside.
Assemble the Sandwiches:
Butter one side of each slice of bread. Place butter-side down on a cutting board. On half of the slices, layer a small handful of cheese, then a generous spoonful of sloppy joe mixture, then more cheese. Top with the remaining bread, butter-side up.
Grill:
Heat a nonstick skillet or griddle over medium heat. Cook sandwiches for 3–4 minutes per side, pressing gently with a spatula, until the bread is golden brown and the cheese is melted. Reduce heat slightly if the bread is browning too quickly.
Rest and Serve:
Let sandwiches rest for 1–2 minutes before slicing. Serve hot with pickles, chips, or a crisp salad.
