Peel the garlic and press it through a garlic press. Stir yoghurt, sour cream, garlic, oil and lemon juice until smooth. Season with salt, pepper and sugar. Clean, wash and drain the lettuce.
Pluck leaves into bite-sized pieces. Clean, wash and thinly slice the mushrooms. Cut camembert into sticks. Wash chives, dab dry and cut into fine rolls.
Arrange salad, mushrooms and camembert on plates. Pour a little sauce over them. Sprinkle with the chive rolls. Serve the rest of the sauce separately. Spread butter on wholemeal bread and serve.