Clean, wash and dice the celeriac. Peel and finely dice the onion. Heat the fat in a pot, fry the onions until transparent and briefly add the celery. Pour in broth, season with caraway seeds and bring to the boil. Cover and simmer for 15-20 minutes. In the meantime clean, wash and dry the celery. Put 4 small sticks from the middle and some green aside.
Cut the remaining sticks into thin slices. Add milk to the cooked celery and puree everything in the broth. Add celery slices to the soup and simmer for another 2-3 minutes. Stir the processed cheese into the finished soup and season with salt and pepper. Garnish with celery green and serve sprinkled with a little caraway. Serve with pretzels and the remaining celery sticks