Peel, wash and dice the potatoes, wash and chop the fennel,
Peel the onions and garlic, wash and cut into small pieces, peel and finely chop the ginger.
Melt the butter in a large saucepan and sauté the onions and garlic in it. Add the potatoes, fennel and ginger and cook for about three minutes, then fill up with vegetable stock and simmer for about 15 minutes with the lid closed.
In the meantime, separate the cress and rinse it clean in a fine sieve.