Add the ground beef, breadcrumbs, onion, egg, allspice, nutmeg, and salt in a large bowl. Mix just until combined. Don’t overmix, or the meatballs will be tough.
Spoon about 1 ½ tablespoons of the mixture or 1 ounce. Form it into a ball and place it on a baking sheet lined with parchment paper.
In a large pan, add olive oil over medium heat. Cook the meatballs for 2-3 minutes on each side. Remove them from the pan and set them aside.
Melt the butter in the same pan over medium heat. Stir in the flour and cook for 2 minutes, stirring continuously, until it browns.
Slowly add the broth while stirring continuously. Then add the milk.
Add the meatballs to the gravy and cook for 10 minutes or until their internal temperature reaches 160 degrees.