In a large cast iron skillet, place the ground beef and cook over medium-high heat, until the crust is seared to a dark brown. Stir the beef and continue cooking it until about 50% of the beef is seared. Place a strainer over a large heat-resistant bowl and strain the beef. Set the beef aside and keep 2 tbsp of the fat.
1 lb. ground beef
Add the two tbsp of beef fat and butter to the skillet. Add the chopped onions, green pepper and mushrooms. Cook, over medium heat, for 1-2 minutes then stir. Cook another 2 minutes until vegetables are just tender.
2 tbsp butter, 1 medium yellow onion, 1 green bell pepper, ½ lb. brown mushrooms
Add the beef to the vegetables and stir.
In a small mixing bowl, whisk together the cornstarch and beef broth.
1 tbsp cornstarch, 1 cup beef broth
Add the beef broth mixture, cider vinegar, ketchup, Worcestershire sauce, salt, pepper, and red pepper flakes to the beef/vegetable mixture.
1 tsp cider vinegar, 2 tbsp ketchup, 2 tbsp Worcestershire Sauce, ½ tsp kosher salt, ½ tsp freshly ground black pepper, ¼ tsp red pepper flakes
Bring to a boil, over medium-high heat. Reduce heat to low and simmer until the mixture has thickened, 5-10 minutes.
Heat oven to broil and while the mixture thickens; butter and toast the insides of the buns. Place the buns, buttered side up, on a foil-lined cooking sheet and broil the insides of buns until golden brown. Transfer the buns to a cooling rack.
6 ciabatta rolls
When the beef mixture has thickened, remove from the heat add the processed cheese. Mix until the cheese has incorporated. Season to taste, if needed.
2-4 tbsp Velveeta
Remove the top buns from the cooking sheet.
Place a large scoop of the meat mixture on top of each bottom bun and cover with 1-2 slices of Provolone cheese. Broil the sloppy Joes just until the cheese melts and transfer the tray to a cooling rack.
4-8 slices Provolone cheese
Replace the top buns and serve. Enjoy!