Mix all the meatball ingredients together. Form little bite sized meatballs. Set aside.
Mix all spaetzle dough ingredients in a bowl, except the butter. Add milk if needed to thin it out. It should be paste like in consistency. Set aside for 2 hours in the fridge.
Saute the celery, carrot, and onion in a big heavy bottom pot or dutch oven in some oil for about 15 minutes. They should be starting to brown and drastically reduced in size.
Add the garlic and cook 3 minutes.
Add in the stock and beets. Bring to a simmer and reduce heat. Cook about 40 minutes until the beets are tender.
Blend soup with a hand blender. Add a little water if needed to thin it out.
Add the meatballs and the cabbage and cover. Simmer on low covered for about 15 minutes. Stir and repeat.
Meanwhile, bring a pot of salted water to a boil. Get any kitchen device that has large holes in it. I used a pizza pan. Place it over the boiling water and put the spaetzle dough on top. Press it through the holes with a spatula. The spaetzle fill fall into the water and cook. Boil the spaetzle for about 8 minutes until you taste one and it doesn't taste grainy.
Strain the spaetzle and toss in a little butter or oil.
Check to see that the meatballs and fully cooked.
Add the mustard to the soup. Taste the soup for seasonings and adjust as needed.
To serve put the spaetzle in a bowl and top with a big ladle of the soup mixture.