Wash the cucumber thoroughly and grate it coarsely. Then mix in a bowl with a little salt and let stand for 15 minutes. Then put the cucumber in a colander and squeeze out any excess liquid. This works quite well with the back of a spoon.
Peel the garlic. Put the cottage cheese, yoghurt, mustard, salt, pepper, the squeezed cucumber and the garlic, squeezed through a press, in a bowl. Mix thoroughly, season again and season if necessary. Let rest for 30 minutes.
Put the tzaziki on a plate. Slice the tomato and egg and garnish the plate with them.