Boil the potatoes. Peel and slice while still lukewarm or cold.
In a saucepan, sauté the finely chopped onion and chopped garlic in some of the 250 ml water. Add the cashew butter and the rest of the water and stir well. Bring the mixture to the boil and season well. The sauce should taste slightly too salty.
Also stir in the oat or yeast flakes. If the sauce is too thick, add more water, if it is too thin, use more cashew butter.
Mix the potatoes, cucumber, herbs and the hot sauce in a large bowl.