Meatball Sliders

Name: Meatball Sliders
Ingredients: 1 tbsp. olive oil; 1/2 c. finely chopped onion; 2 clove garlic; 3 slice White bread; c. milk; 3/4 lb. ground beef chuck; 1/2 lb. ground pork; 1/4 lb. ground veal; 1/2 c. freshly grated Parmesan or Pecorino Romano cheese; 1 large egg; 2 tbsp. chopped fresh basil or Italian parsley; 1/2 tsp. Kosher salt; 1/2 tsp. Freshly ground black pepper; 3 c. homemade or store-bought marinara sauce; 1 1/2 c. baby arugula; 1 package party-size potato rolls; 10 slice provolone cheese