Thoroughly wash and clean the mussels and remove the barbs. Remove opened mussels. Peel, wash and slice the carrots. Peel, wash and slice the onions.
Clean and wash the leek and cut into fine rings. Heat the oil and add the mussels to the pot. Add the carrots, onions and leeks and pour on the vegetable stock. Steam for 7-8 minutes with closed lid.
Refine with white wine and boil up briefly. Fill mussels with some stock into soup plates and serve with toast.