Stir the breadcrumbs and milk together in a large bowl. Let the mixture rest for 5 minutes.

Add the egg, onion, salt, black pepper, allspice, and nutmeg. Stir until combined.

Add the ground beef and pork. Mix gently with your hands just until everything comes together. Do not overmix.

Shape into approximately 28 to 32 meatballs, about 1¼ inches each.

Heat the olive oil and 1 tablespoon butter in a large skillet over medium to medium-high heat.

Brown the meatballs in batches, turning occasionally, for about 6 to 8 minutes. Add the remaining tablespoon of butter if needed. The centers don't have to be fully cooked yet.

Transfer the browned meatballs to a plate.

Reduce the heat to medium and add 3 tablespoons butter to the same skillet.

Whisk in the flour and cook for 1 to 2 minutes.

Gradually pour in the beef broth while whisking and scraping the browned bits from the bottom of the skillet.

Stir in the Worcestershire sauce and Dijon mustard.

Simmer for 3 to 4 minutes until the gravy begins to thicken.

Reduce the heat and stir in the heavy cream.

Return the meatballs and any accumulated juices to the skillet.

Partially cover and gently simmer for 6 to 8 minutes, until the meatballs are cooked through and reach 160°F internally.

Meanwhile, cook the egg noodles in salted boiling water according to the package instructions until just tender.

Drain the noodles and toss them with 1 tablespoon butter.

Reduce the skillet to very low heat or briefly remove it from the burner. Stir the sour cream into the meatball gravy until smooth.

Taste and adjust the salt and pepper. If the sauce is too thick, stir in a small splash of beef broth.

Spoon the buttered egg noodles onto plates, add the meatballs, and generously ladle the creamy gravy over everything.

Sprinkle with chopped parsley and black pepper if desired and serve immediately.