1. Wash sweet potatoes and boil them for 15 to 20 minutes. Strain off water and leave to cool.
2. Meanwhile, wash and pat dry the zucchini and the eggplant. Clean mushrooms. Peel and quarter onions. Wash the sage, shake off the remaining water and pick off the leaves.
3. Peel sweet potatoes, cut in half lengthways and cut into thick pieces. Stick potatoes and vegetables onto the skewers.
4. Heat olive oil in a big pan and fry skewers for approx. 10 minutes on all sides. Add sage leaves just before the end. Season skewers with salt and pepper and arrange on plates. Sprinkle with balsamic crème and sage. Serve with sour crème.
Preparation time: approx. 1 hour