Scrub potatoes thoroughly in cold water, wash and drain. Heat 5 tablespoons of oil in a frying pan and fry the potatoes covered for about 10 minutes. In the meantime, wash and drain the garlic, rosemary and chillies.
Pluck rosemary roughly from the stem. Remove the lid and fry the potatoes for a further 10-15 minutes, turning. Add garlic, rosemary and chilli 5 minutes before the end of the cooking time and fry. Meanwhile, peel the onion and cut into fine slices.
Mix vinegar, salt, pepper and mustard and fold in the remaining oil. Add the onion. Clean and wash the salad and cut into strips, except for 2 leaves for garnishing. Clean, wash and halve the tomatoes.
Mix the lettuce and tomatoes with the vinaigrette and arrange on a deep plate with the lettuce leaves. Place the potatoes in a bowl and garnish with fresh rosemary. Serve with lettuce and sour cream.