Soak the breadcrumbs in the milk for 5 minutes, then mix with the beef, pork, egg, onion, salt, allspice and pepper and roll 32 meatballs.
Brown the meatballs in the oil in 2 batches for 6 minutes and transfer them to a 6-quart crockpot.
Whisk the broth and flour until smooth, pour it over the meatballs, and cook covered on low for 4 to 5 hours until they reach 160°F.
Cook the egg noodles separately and divide them among 8 bowls.
Switch off the crockpot, temper the sour cream with 1 cup hot gravy, stir it back in, and spoon the meatballs and gravy over the noodles.