Peel the potatoes, put them in a pan and cook for about 20 minutes. Drain the water and let the potatoes cool down. Alternatively, boiled potatoes from the previous day can be used.
Cook the cauliflower remains in water for about 10 to 15 minutes until soft. Pour the boiled cauliflower remains into the mixer with a little bit of the cooking water and puree finely. Pour the puree into a cotton cloth and wring out the liquid. Put the liquid aside for the béchamel sauce.
ADD the cauliflower mixture with spelt flour, salt and vegan margarine in a bowl. Mix everything into a dough. If the dough is too dry, add a little water or cauliflower liquid. Cover the bowl and put the dough in the fridge for about 20 minutes.
Preheat oven to 220° Celsius.
In the meantime, prepare the béchamel sauce. Melt 25g margarine in a pan. Add the flour and mix well until the mixture is yellowish-lumpy. Then add the cauliflower liquid and the cream in several steps, stirring well to avoid lumps. Bring the béchamel sauce to the boil briefly and set aside. Season with salt, white pepper and nutmeg.
Roll out the dough thinly on a floured surface, transfer into a cake tin and press down well. Use a fork to make a tight piercing in the base of the dough. Blind bake the cake dough on the lowest groove of the oven for approx. 10 minutes.
In the meantime, cut the potatoes into thin slices.
Remove the cake dough from the oven. Spread the potato slices on the cake base and pour the béchamel sauce over the quiche. Place in the oven again for about 15-20 minutes. If you want to brown the béchamel sauce a little, bake the cake on the top groove for the last 5 minutes.