To make the meatballs, peel and grate the onion and carrot and add them to a large bowl together with the beef and egg.
Cut the slice of bread into cubes, and soak in milk. Squeeze out the excess milk and add the bread to the other ingredients.
Season with salt, pepper, add the allspice, parsley and vegetable oil and mix well to combine.
Shape out meatballs, depending on their size you should get more or less 24 meatballs.
Cover them with flour, shaking any excess off them, arrange on a baking tray, spray deliberately with cooking oil, and bake in the pre-heated oven at 180 degrees Celsius (360 Fahrenheit) for 30 minutes.
In a pan, add the butter and allow it to melt. Whisk in the flour and stir for 30 seconds, then add the beef stock and continue to stir until it thickens slightly.
Mix in the sour cream and the black pepper, and stir for about 2-3 minutes.
Add the meatballs and stir for a further 2 minutes.
Remove from the heat and garnish with fresh parsley. Serve immediately with pasta.