Combine milk and breadcrumbs in a small bowl. In another large bowl, whisk the egg and add meat, onion, and salt. Add the soaked breadcrumbs to the meat mixture and gently mix with your hands until evenly combined.
Shape into small meatballs. Not too tight. You want to lightly roll them between your hands to form a ball that feels like it will hold together, but lightly so they will absorb the sauce. Then roll each meatball in GF flour.
Heat oil in a large, deep skillet over medium-high heat. Add the meatballs and gently brown on all sides, about 5 to 7 minutes. Once all of the meatballs are cooked, transfer to a bowl. Drain oil.
For Gravy: Next whisk together 4 tablespoons of gluten free all purpose flour plus 4 tablespoons of butter in the same skillet until the mixture is thick and smooth. Continue to stir and slowly brown the flour over a low heat for 5 minutes.Then add 3 cups of stock. Whisk and simmer so that the gravy stays smooth while it thickens.Season with salt and pepper to taste.
Return the meatballs to the skillet along with any juices, cover, and simmer in your gravy. Serve over gluten free noodles.