Add ground meat, parmesan, egg, garlic, parsley, onion flakes, oregano, fennel, red pepper flakes, salt, and pepper. Gently mix by hand until combined.
Using a small cookie scoop (about 2 teaspoons) form meat into tight balls. Set aside on a plate or piece of foil.
Select saute on the pressure cooker and add oil. When hot, add onion and saute until softened, 4 – 5 minutes. Add garlic and stir for 1 minute.
Add broth, crushed tomatoes, basil, Italian seasoning, oregano, red pepper flakes, salt, pepper, and parmesan rind (if using), stir.
Gently add meatballs to the pot.
Secure the lid and turn pressure release knob to a sealed position. Cook at high pressure for 3 minutes.
When cooking is complete, use a quick release.
Remove what’s leftover from the parmesan rind and add spinach to the hot soup and stir in to wilt.
To serve, ladle into bowls and top with a mixture of mozzarella and parmesan cheese.
To really take it over the top, use oven safe bowls and place it under the broiler until the cheese is golden brown.
Serve with toasted slices of bread for dipping and scooping!
To make this a quick freezer meal, I like to double the meatball ingredients, form the meatballs, and freeze them on a sheet pan. Once frozen, place them in a freezer safe ziplock.
When ready to cook, add meatballs to the soup ingredients and cook for 5 minutes instead of 3 minutes.
You can also saute twice the amount of onions and garlic and freeze half of them as well so they are ready to simply throw into the pot with the cooking liquid and frozen meatballs.
Use a low fat meat to prevent the soup from being overly greasy. Pack the meatballs tight so they don’t fall apart in the soup.
Freeze leftovers by pouring them into a freezer safe ziplock, pressing out the air, and freezing flat. To prepare from frozen, let thaw overnight in the fridge or add frozen ingredients to the pressure cooker with 1/4 cup water or broth, then cook at high pressure for 3 minutes. Use saute to heat the rest of the way if needed.