Basically, ground beef mixed with uncooked rice, some minced onion, salt & pepper, rolled into meatballs, and put in the pressure cooker with tomato soup and a little water.
This is basically Grandma's recipe:
Porcupine meatballs - allrecipes.com, though she called for half the rice, and the same amount of pepper as salt. We've always made them in a pressure cooker. The recipe I have calls for 10 min at 15 lbs, let the pressure come down on it's own; or 15 min at 15 lbs, and release the pressure right away. I put them in the Instant pot on normal pressure for 15 minutes, and usually release the pressure manually.
They're definitely comfort food in our family. Sometimes served over mashed potatoes (mmmmmm!).