In a large bowl, combine the onion, garlic, parsley, breadcrumbs, Parmesan, eggs, milk, red pepper, flakes, oregano, Italian seasoning, salt and pepper. Stir to combine thoroughly before adding the meat.

Then add the meat to the breadcrumb mixture.

Form the meatballs, using the size of your dinner rolls as a guide. I made mine a little bigger than a golf ball.

Broil the meatballs at 400 degrees for 15-20 minutes, until they're golden brown, flipping them once during cooking.

While the meatballs cook, heat up the marinara sauce in a saucepan on medium heat.

After the meatballs are browned, remove them from the oven and place them into the hot marinara sauce.

Lower the heat and simmer the meatballs for another 15 minutes.

Toast the slider buns until they're slightly golden, then place the bun bottoms onto a baking sheet.

Place a meatball onto each bun, and top each meatball with a generous sprinkle of mozzarella cheese.

Broil the meatballs at 400 degrees F for 3-5 minutes, just until the cheese is melted.

Place a bun top onto each slider, then serve.