Wash and clean the cucumber, dab dry and cut into thin slices. Wash parsley, dab dry and chop finely. Season vinegar with salt, pepper and sugar. Gradually add the oil.
Stir in the parsley. Mix cucumber slices and vinaigrette. Knead minced beefsteak, egg, breadcrumbs and quark. Season with curry, salt and pepper. Form 20 small balls with wet hands. Heat oil in a pan and fry the balls for about 10 minutes.
In the meantime, wash mint, dab dry and chop finely. Peel garlic and press it through a garlic press. Mix mint, garlic, yoghurt and lemon juice. Season to taste with salt and pepper.
Serve meatballs with yoghurt mint sauce and cucumber salad. Cut flatbread diagonally into strips and serve.