Melt 2 tablespoon butter in a medium or large saucepan over medium heat, and add onions. Saute until translucent and beginning to brown, about 10 minutes.
2 tablespoon butter, salted, 8 oz onion, diced
Preheat oven to 350°F. Add ground beef and stir regularly until cooked through, about 10 more minutes.
1 lb Ground beef, 85% lean
Meanwhile, combine ketchup, worchestershire sauce, brown sugar, chili powder, dried mustard, salt and pepper and mix until well combined.
¾ cup ketchup, 1 tablespoon Worcestershire sauce, 1 tablespoon brown sugar, 1 teaspoon chili powder, ½ teaspoon dried mustard, ½ teaspoon salt, ¼ teaspoon black pepper
Drain beef and onion mixture of excess fat with your preferred method- I recommend a paper towel for ease. If desired, deglaze the pan with a touch of water.
Add all but a few tablespoons of the sauce to the meat mixture. Stir aggressively to deglaze with the sauce, and allow mixture to cook down for about 8 minutes. If thicker than desired, add in remaining sauce, otherwise reserve it for dipping.
Slice the slider rolls horizontally as one large roll. Set the tops to the side and set the bottoms in a greased 9x13 pan. Layer half of the cheese on the bottoms, and spread sloppy joe mixture on top of the cheese, then layer remaining cheese on top of the mixture.
12 oz Hawaiian Rolls, 6 oz provolone cheese
Place the roll tops back on top and if desired, melt butter and combine with dried mustard. Spread over rolls with a pastry brush and sprinkle with sesame seeds. Bake until golden brown and the cheese melted, about 10 minutes.
2 tablespoon butter, salted, ¼ teaspoon dried mustard, ½ teaspoon sesame seeds