For the hummus, drain the chickpeas, rinse with cold water and drain. Peel garlic and chop coarsely. Puree the chickpeas, tahini, garlic and 2 tbsp. oil with a hand blender. Season hummus with salt and lemon juice.
Mix yoghurt and sour cream for the tzatziki. Peel garlic, crush finely and stir into the yoghurt cream. Season to taste with salt and pepper. Wash the cucumber, peel and grate if necessary.
For the salsa, finely dice the olives. Peel and finely dice the shallot. Mix olives, shallot, 1 tsp. oil and lemon peel and juice. Season to taste with salt, pepper and sugar.
For the meatballs, knead the mince, egg and breadcrumbs. Season with about 1 teaspoon salt and about 1⁄2 teaspoon pepper. Form 4 flat meatballs from the mixture. Heat 2 tablespoons of oil in a frying pan. Fry the meatballs for 3-4 minutes on each side.
Cut open the buns. Spread hummus on the lower halves and sprinkle with salsa. Place the meatballs on top. Squeeze the cucumber if necessary. Add 1 blob of tzatziki and some cucumber. Place the upper halves of the rolls on top.