Boil the white praws with salt. Withdraw it right when it starts boiling. Save one glass of the water.
To stop the heat, introduce the praws in water with ice. Drain them, peel them and save them for later.
Cook the chopped potatoes for 15-20 minutes in the water you used for the praws. Drain them and put them aside.
For the mayonaisse, whip the egg, the sunflower oil, the lemon juice and the glass of water you saved earlier.
Chop the peeled praws in small pieces and save some for decoration.
Mix all the ingredients and serve.