Soak breadcrumbs in milk for 5 minutes, then mix with ground beef, pork, egg, grated onion, allspice, nutmeg, and salt.
Roll into small 1-inch balls.
Melt butter in a large skillet over medium-high heat and brown meatballs in batches on all sides. Remove and set aside.
In the same skillet, whisk flour into the remaining butter and cook 1 minute, then gradually whisk in beef broth and heavy cream.
Add Worcestershire sauce and simmer sauce for 3-4 minutes until thickened.
Return meatballs to the pan and simmer in the sauce for 8-10 minutes.
Garnish with fresh parsley and serve with toothpicks.