Mini Sloppy Joes with Pulled Pork

Name: Mini Sloppy Joes with Pulled Pork
Ingredients: 2 tablespoons unsalted butter; 1 cup finely chopped onion; 0.66666668653488 cup finely chopped green bell pepper; 1 cup beef stock; 1 cup ketchup; 1 tablespoon brown sugar; 1 tablespoon Worcestershire sauce; 1 tablespoon whole-grain mustard; 4 cloves garlic, minced; 1 teaspoon chili powder; 2 cups cooked pulled pork without sauce; 3 dashes hot pepper sauce (such as Tabasco®), or to taste; salt and ground black pepper to taste; 10 mini-Kaiser rolls, sliced and warmed