Stir the breadcrumbs and milk together and let them stand for 5 minutes until the liquid is absorbed.
Mix in the beef, pork, egg, onion, salt, allspice and nutmeg and shape into 24 small meatballs.
Melt 1 tablespoon butter in a large skillet over medium-high heat and brown the meatballs in 2 batches for 6 minutes per batch; transfer them to a plate.
Melt the remaining butter, stir in the flour for 1 minute and whisk in the broth and cream until smooth.
Return the meatballs and simmer for 8 to 10 minutes until they reach 160°F and the gravy lightly thickens.