Clean the fennel bulb to remove dirt and cut in quarters lengthwise. Thinly slice each quarter.
Peel and cut the onion in half and slice thinly.
Peel and wash the potatoes. Cut into 1 cm (1/2 inch) cubes and leave to rest in cold water.
Wash the chard. If there are any bigger leaves, cut away the stems. You'll be cooking those separately.
Add a tablespoon of olive oil to a hot pan and add sliced onions and fennel. Sauté for 10 minutes or until they turn golden. Make sure to stir now and then to prevent burning.
Drain the potatoes and add them to the fennel and onions. Add the separate stalks from the chard at his point too. Add boiling water and cover the pan. Reduce the heat to low and let cook for 10 minutes or until the potato is fork-tender.
Add the rest of the chard, cover and cook for two to three minutes. Remove from the heat and pour everything in a blender. Add heavy cream, salt, and pepper and blend until the soup is smooth and silky. Add more boiling water if necessary.
Garnish with some olive oil, heavy cream, and seeds. Serve warm.