Crumble the yeast and mix with sugar until the yeast is liquid. Put flour, 1/4 teaspoon salt, oil and 175 ml lukewarm water into a bowl. Add the mixed yeast and immediately knead into a smooth dough using the dough hooks of the hand mixer. Cover the dough and let it rise in a warm place for about 1 hour.
For the crème, mix crème fraîche and harissa, season with salt. Peel onions and cut into slices. Peel potatoes and slice them very thinly
Quarter the dough. Roll out 1 quarter thinly on a floured work surface. Place on a baking tray lined with baking paper and cover with 1/4 of the cream, potatoes and onions
Bake in the preheated oven (electric cooker: 250 °C/ convection oven: 225 °C/ gas: see manufacturer) for approx. 10 minutes. Do the same with the remaining ingredients. In the meantime wash parsley, shake dry, pluck leaves from the stalks and chop. Sprinkle the finished tarte flambée with parsley
waiting time approx. 3/4 hours