In a large mixing bowl, add half of the onion, half of the garlic, basil, Parmesan cheese, kosher salt, and red pepper flakes. Whisk in the eggs. Add ground turkey, ground beef, and soaked breadcrumbs. Gently mix with your hands until well combined.
½ large yellow onion, 4 cloves garlic, ½ cup fresh basil, ½ cup parmesan cheese, 1 teaspoon kosher salt, ¼ teaspoon red pepper flakes, 2 large eggs, 1 pound ground beef, 1 ¼ pounds ground turkey