Heat butter and oil in large skillet over MED/MED-HIGH heat.  Add beef and brown, breaking apart into crumbles as it cooks, about 5 minutes.  Transfer to colander to drain.

Add onion and bell pepper to same skillet and cook 2-3 minutes, until soft.  Add garlic and cook 30 seconds or so, until fragrant.  Add beef back to the skillet and add tomato paste.  Stir well.

Add ketchup, water, brown sugar, mustard, chili powder, Worcestershire sauce, salt, red pepper flakes (if using), and black pepper.  Stir well to combine.

Cook over MED heat for 10-15 minutes, until mixture has thickened to your liking.  Remove from heat and serve over toasted buns.

Nutrition Disclaimer:

The Chunky Chef is not a dietician or nutritionist, and any nutritional information shared is an estimate. If calorie count and other nutritional values are important to you, we recommend running the ingredients through whichever online nutritional calculator you prefer. Calories can vary quite a bit depending on which brands were used.