First Step: Preheat oven to 350°F (175°C). Grease the bottom of a rimmed baking sheet with butter. This prevents sticking and adds flavor to the bottom buns in your chopped cheeseburger sliders.

Second Step: Heat the 1/2 tablespoon olive oil in a large skillet over medium-high heat. Add the 1/2 large onion, finely diced, and 2 lb lean ground beef. Season right away with 1 teaspoon salt, 1 teaspoon black pepper, and 1 teaspoon garlic powder. Break up the beef as it cooks for that signature chopped texture in ground beef sliders.

Third Step: Sauté the mixture until the beef cooks through, about 10-12 minutes. Stir often to chop finely. Remove from heat and spoon off any excess fat. This tip keeps your sliders for a crowd from getting soggy. Lean beef helps here too.

Fourth Step: Stir in 1/4 cup mayonnaise while warm. It melts into the beef, creating a creamy binder that makes every bite in these mini cheeseburger sliders juicy and flavorful. Let cool slightly for easier assembly.

Fifth Step: Slice the 24 dinner rolls in half. Place the bottom halves on the prepared baking sheet in a single layer. Layer each with one of the 8 slices medium cheddar cheese. This cheese barrier protects buns from moisture, a pro move for party appetizer cheeseburger sliders.

Sixth Step: Spread the beef mixture evenly over the cheese layer. Divide it to cover all rolls without piling high. Then sprinkle 6 oz shredded medium cheddar (or extra slices) on top of the beef. More cheese ensures melty goodness throughout.

Seventh Step: Place the top halves of the buns, cut-side down, over the beef. Brush the tops generously with 2 tablespoons melted unsalted butter. Sprinkle 1 tablespoon sesame seeds on top right after buttering so they stick well.

Final Step: Bake uncovered for 12-15 minutes, until cheese melts fully and tops turn golden brown. Watch closely to avoid over-browning. Let rest 2-3 minutes before pulling apart into individual chopped cheeseburger sliders. Serve warm for game day or potluck wins.