Mix all the ingredients for the meatballs together in a bowl. Mix thoroughly to ensure everything is well combined.
Once the mixture is worked together, shape into even round balls. You will find this easier to do if you keep your hands damp with a little cold water. Try to make the meatballs as even as possible as this helps with the cooking.
Place meatballs in oven proof dish. Bake 20-25min or until tested and it is well done cooked. Remove from the oven and set aside.
Heat the oil in a medium pot. Add the onions and mushrooms and cook gently for 5 minutes taking care not to burn.
Add the garlic and cook for a further 2 minutes until both the garlic, mushroom and onions are translucent.
Add the rosemary, beef stock and wine.
Bring the sauce to the boil, then reduce the heat to simmer for 2 minutes. Remove from heat and pour over meatballs. Serve immediately.