1 Mix together quark and yogurt in a bowl until smooth.
2 Peel cucumber, halve lengthwise, remove seeds and cut cucumber into small cubes. Peel onion and chop finely. Squeeze juice from lemon half.
3 Rinse dill, shake dry, pluck fronds and chop finely. Mix dill, cucumber and onion into yogurt mixture. Season with salt, pepper and 1-2 tablespoons lemon juice. Gently fold in cooked shrimp.
4 Toast bread slices on rack of preheated oven at 200°C (fan: 180°C, gas: mark 3) (approximately 400°F) until lightly golden and crisp, 4-5 minutes. Remove rack from the oven and allow bread to cool on it.
5 Just before serving, rinse apple, wipe dry, peel and core. Cut apple into thin strips and fold into shrimp salad.
6 Cut cress from the bed with kitchen shears, sprinkle over salad and serve with toasted bread.