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. 

Heat a second skillet over medium high heat. Butter 2 pieces of bread on one side.

In a ungreased skillet place one piece of bread, butter side down. Let cook a minute or two. Add a slice of cheese of your choice. I like sharp cheddar.

Then add a scoop of the sloppy joe mixture on top of the on top of the cheese slice.

Top with slice of bread, butter side up. Flip the sandwich over so the done side is facing up and the buttered side is down. Cook till browned to your desired doneiness. Serve with chips or French fries. I like coleslaw to.