Wash potatoes thoroughly and cook in boiling water for about 20 minutes. In the meantime, clean and wash the radishes and cut them into sticks. Wash the cucumber and cut it into sticks as well. Peel and chop the onion. Mix spring quark, milk, radishes, cucumber and onion. Drain the potatoes, let them drip off and arrange on plates with matie and spring quark. Serve garnished with fresh herbs as desired