1. Chop all vegetables into medium-sized pieces (feel free to skip or swap vegetables according to your preference).
2. Heat oil and sauté onion first, then add mushrooms, peppers, celery root, kohlrabi and carrots and cook until soft. Add eggplant when vegetables are partially cooked so it doesn’t become too soft.
3. In a separate bowl, mix tomato paste, flour, and 1/4 cup water until smooth. Pour over vegetables and cook for an additional 10 minutes.