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 is thoroughly browned, approximately 5-6 minutes. Remove from heat and carefully drain any excess fat from the skillet.

Tip: To prevent flare ups, make sure no grease drips down the side of the skillet if cooking with gas heat.

Return to heat and add tomato sauce, tomato paste, Worcestershire sauce, brown sugar, mustard, and chili garlic sauce. Season with additional salt and black pepper, if desired, and stir thoroughly to combine. Simmer, uncovered, until heated through, approximately 5-10 minutes.

While the 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!