Heat olive oil in a large, high-sided skillet over medium heat. Add onion, minced garlic, and green pepper. Season with salt and black pepper, to taste, and stir to combine. Sauté for 4-5 minutes, or until the vegetables soften and start to develop some color.

Add the ground beef and break into small pieces with a spatula. Cook until the meat mixture is thoroughly browned. Do it for approximately 5-6 minutes. Remove from heat and carefully drain any excess grease from the large skillet.

Return to medium-high heat and add the rest of the ingredients: tomato sauce, tomato paste, Worcestershire sauce, brown sugar, mustard, and chili garlic sauce. Season with additional salt and black pepper, if desired. Stir it thoroughly to combine. Simmer, uncovered, until heated through for approximately 5-10 minutes.

While the sloppy joe meat simmers, place the top oven rack in the second from highest position and pre-heat the oven broiler to high. Open the hamburger buns and arrange on a large, rimmed baking sheet. Brush each surface with the melted butter and place the baking sheet under the broiler for several minutes, rotating once halfway through, or until the buns are golden brown.

Remove the baking sheet from the oven and spoon some of the warm meat sauce onto the bottom portion of each bun. Cover and serve immediately with your choice of sides. Enjoy!