Wash the potatoes and cook in boiling water for 15-20 minutes. Then rinse with cold water, peel and cut in half. In the meantime clean and wash the tomatoes, zucchini, spring onions and mushrooms.
Cut tomatoes into quarters, zucchini and spring onions into bite-sized pieces. Put prepared ingredients alternately on skewers. Strip rosemary needles from the branch. Finely chop the chervil. Heat oil just before serving.
Fry the skewers in it all around for about 8 minutes. Season with salt and pepper. Swirl rosemary and half of the chervil in the cooking fat. Wash and chop the remaining herbs. Peel and finely chop the onion. Mix chopped herbs, diced onion and quark.
Season to taste with salt and pepper. Serve skewers and herb quark garnished with fresh herbs.