• Heat oil in a large stock pot over medium-high heat and cook onion for about 5 minutes until softened. Stir in carrot and cook for another 5 minutes. Stir in celery root, garlic and red pepper and cook for another minute.
• Pour in the vegetable stock or water, adding chili pepper if desired, salt and pepper and bring the mixture to a boil. Reduce the heat to a gentle simmer and cook for roughly 20 minutes until the vegetables reach a tender consistency.

Prepare the meatballs.

• While the soup simmers, prepare the meatballs. Combine the ground meat, semolina flour, egg, uncooked rice, salt, pepper, and chopped fresh parsley in a medium bowl. Shape the mixture into 1-inch (2.5 cm) balls using a cookie scoop and wet hands, then place them on a plate.
• Carefully transfer the meatballs to the simmering soup along with the potatoes. Allow it to return to a boil, then reduce the heat and simmer for an additional 20 minutes until the potatoes are tender and the meatballs are fully cooked.
• In a medium bowl mix sour cream with the egg yolk and minced garlic. Add 2 ladles of hot soup, stir well and add to the pot.
• Let it boil for 1 minute before finishing with fresh herbs such as lovage or parsley, as well as salt and pepper to taste.
• Remove from heat and serve hot alongside crusty bread. Enjoy!