Mix meatballs (5 min): Add the ground beef, Italian sausage, shallot, garlic, parsley, Italian seasoning, salt, and cheese. Use clean hands to mix everything together until all of the ingredients are well distributed. Do not over mix or it can make the meatballs tough. The mixture should be wet but still hold its shape.
1 lb ground beef, 1/2 lb mild Italian sausage, 1 small shallot, 4 cloves garlic, ¼ cup finely chopped fresh parsley, 2 teaspoons Italian seasoning, ¼ teaspoon red pepper flakes, ½ tsp kosher salt, 1/2 cup grated pecorino romano cheese