Preheat the oven to 350 degrees Fahrenheit. Grease a 9x13 pan using nonstick cooking spray.
Combine the beef, chopped onions, brown sugar, garlic powder, sea salt, and black pepper in a large skillet over medium heat. Use a spatula to break up the meat until there are no large chunks left. You're looking for a fine mince. Cook until the beef is browned.
1 pound ground beef, 1/4 cup yellow onion, 2 teaspoons brown sugar, 1/2 teaspoon garlic powder, 1 teaspoon sea salt, 1/4 teaspoon black pepper
Pour the beef broth, ketchup, and yellow mustard into the pan. Fold into the meat mixture.
1/2 cup beef broth, 3/4 cup ketchup, 1 teaspoon yellow mustard
In a separate bowl, mix the water and cornstarch. Slowly add it to the beef and sloppy joe sauce mixture while stirring to combine. This will slightly thicken the sauce.
2 tablespoons cornstarch, 2 tablespoons water
Place the dinner rolls on a cutting board or a flat surface. Using a large knife, slice the rolls in half all at once. Place the bottom half of the rolls in the greased baking dish.
1 package King's Hawaiian Rolls
Spoon the beef onto the bottom buns, then use the back of the spoon (or a spatula) to spread into an even layer.
Spread the shredded cheese over the sloppy joe mix.
1 1/2 cups sharp cheddar cheese
Add the top layer of the rolls.
Using a separate small bowl, combine the melted butter, sea salt, sesame seeds, and freshly chopped thyme. Spoon this over the top of the rolls evenly. You can use a basting brush, if needed.
1/4 cup butter, 1/2 teaspoon sea salt, 2 teaspoons sesame seeds, 2 teaspoons fresh thyme
Cover the baking dish with aluminum foil and bake for 15 minutes, until the cheese is melted and the sloppy joe meat is fully cooked.
Turn the oven to broil, remove the foil, and allow the tops of the buns to toast for about 2-3 minutes. Serve warm and enjoy.