Wash the potatoes and cook in plenty of boiling water for about 20 minutes. In the meantime, roughly chop the walnuts and roast them in a pan without fat, remove them. Rinse potatoes under cold water, drain and peel.
Cut the potatoes into slices. Heat clarified butter in a large pan. Fry the potatoes for about 10 minutes while turning. In the meantime wash and halve the tomatoes. Clean and wash spring onions and cut them into rings.
Wash the thyme and dab dry. Wipe off the leaves. Add spring onions, tomatoes and thyme to the potatoes. Season with salt and pepper and fry for another 3 minutes. Sprinkle with walnuts.