Add the cubed bread and milk to a large bowl. Let the bread soak for 10 minutes.
While the bread is soaking, heat 1 tablespoon of the olive oil in a large skillet over medium heat. Add the onion and saute for 2-3 minutes, until softened. Remove from heat and set aside to cool slightly.
Add the ground beef, ground pork, egg, salt, pepper, allspice, nutmeg, and garlic powder to the bowl of bread and milk, along with the cooled onions. Mix well with your hands until combined.
Form about 30 small meatballs (each about 1" in diameter) and set aside on a baking sheet or plate.
Heat the remaining tablespoon of oil and tablespoon of butter over medium-high heat in the same skillet used for the onions. Working in batches, fry the meatballs for about 4-5 minutes, rotating to brown on all sides. Transfer to a plate and keep warm.
Once all of the meatballs are browned, make the sauce in the same pan by heating ¼ cup butter until melted. Whisk in the flour and cook for about 2 minutes until light brown and bubbly.
Whisk in broth, cream, Worcestershire sauce, salt, and pepper. Bring to a simmer and cook, stirring frequently, for 1-2 minutes until slightly thickened.
Return the meatballs to the pan with the sauce, then reduce the heat to medium-low and continue to simmer for 8-10 minutes until the meatballs are cooked through.
Garnish with chopped parsley and serve over mashed potatoes, rice, or egg noodles.