In a mixing bowl combine 1 pound lean ground beef (90/10), 1/4 cup breadcrumbs, 1/4 cup grated Parmesan cheese, 1 large egg, 2 cloves garlic (minced), 1/2 teaspoon salt, 1/4 teaspoon black pepper, and 1 tablespoon fresh parsley (chopped). Mix gently until just combined—do not overwork the meat.
Form the mixture into 1 1/2-inch meatballs and set them aside on a plate or baking sheet.
Pour 1 cup low-sodium beef broth into the Instant Pot. Place a trivet or steamer basket inside the pot.
Arrange the meatballs on the trivet (in a single layer if they fit; it’s okay if they touch or stack slightly).
Pour 24 ounces marinara sauce over the meatballs so they are evenly covered.
Secure the Instant Pot lid and set the valve to SEALING. Select Pressure Cook (or Manual) on HIGH pressure and set the time for 7 minutes.
When the cook time ends, allow a natural pressure release for 5 minutes. After 5 minutes, carefully move the valve to VENTING to quick-release any remaining pressure.
When the float valve drops and the pressure is fully released, open the lid away from your face. Serve the meatballs with the sauce.