Peel, wash and cut the potatoes into pieces. Cook in boiling salted water for about 15 minutes. Peel and chop onion and garlic. Remove chard leaves from the stalk, wash, cut stalks into pieces, cut leaves into wide strips.
Heat the oil in a pot and fry the onion, garlic and chard stalks. Add 1.25 litres of water, bring to the boil and stir in the stock. Simmer covered for 5 minutes. Drain the potatoes and let them drain.
Wash, clean and seed the tomatoes and cut into small cubes. Roast the pine nuts in a pan without fat until golden brown, take them out. Add chard strips to the soup and simmer for another 5 minutes.
Add crème légère, potatoes and tomatoes to the soup and bring everything to the boil once. Season to taste with salt and pepper. Serve the soup sprinkled with pine nuts and parmesan.