Wash the potatoes thoroughly, cover and cook in plenty of boiling water for about 20 minutes. Lightly roast pumpkin seeds in a pan without fat, remove and let cool off. Quarter onion and cut into fine strips. Drain potatoes, rinse with cold water and let them drain. Peel and slice the hot potatoes.
Heat 5 tablespoons of water, vinegar and onion in a small pot, stir in broth. Season vinaigrette with salt, pepper and sweetener. Fold in sunflower oil. Pour the vinaigrette over the warm potato slices and mix carefully. Drain the potatoes for at least 30 minutes and let them cool down
Wash lamb's lettuce thoroughly and drain. Season potato salad with salt and pepper again. Fold in lamb's lettuce, ham and pumpkin seeds. Sprinkle with balsamic vinegar