In a large skillet, melt the butter and oil over a MED/MED-HIGH heat.
Then, add the ground beef to brown and break them apart into crumbles as it cooks for about 5 minutes.
Drain the beef by transferring it into a colander.
In the same skillet, add the onions and bell pepper to cook for about 2-3 minutes.
Then, add the garlic to cook until fragrant, about 30 seconds or so.
Add the beef back into the skillet followed by tomato paste and mix everything together.
Then add the ketchup, water, brown sugar, mustard, chilli powder, Worcestershire sauce, salt, red pepper flakes and black pepper. Stir well to mix everything together.
Continue cooking over MED heat for 10-15 minutes until desired consistency is achieved.
Remove from heat and serve over toasted buns.
To toast the buns, add a drizzle of vegetable oil on to a clean skillet and set the heat on high. Once the oil is hot, add the buns and toast them to your liking. Place them on a cooling rack while cooking the filling, so they are ready to be served.
Notes
You can use any type of buns to your liking, but Pretzel buns or Brioche buns are most suitable for sloppy joes.
You can choose to opt out or adjust spices that you dislike according to your liking. However, note that this will disrupt the final taste of your sloppy joes.