Wash the potatoes and cook in boiling salted water for 15-20 minutes. Pour off, rinse with cold water, peel, cool slightly and cut into slices. Wash and peel the asparagus and cut off the woody ends. Cut asparagus into bite-sized pieces and cook in boiling salted water at medium heat for about 15 minutes. For the pesto, clean, wash and roughly chop the watercress. Wash and finely chop the dill.
Peel garlic and press it through a garlic press. Roast pine nuts in a pan without fat until golden brown. Puree cress, dill, garlic, pine nuts, olive oil and parmesan in a blender. Season to taste with salt, pepper, vinegar and sugar. Mix pesto, potatoes and asparagus and let it stand for a while. Serve garnished with nasturtiums and dill umbels