Crumble the yeast and mix with sugar until the yeast becomes liquid. (This saves the pre-dough.) Put flour, 1/4 teaspoon salt, oil and 150 ml lukewarm water in a bowl. Add mixed yeast and knead immediately to a smooth dough. Cover the dough and let it rise in a warm place for about 30 minutes. In the meantime, clean, wash and cut spring onions into rings. Quarter bacon slices.
Wash thyme, shake dry and pluck leaves from the stalks. Mix sour cream and crème fraîche, season with thyme, salt and pepper. Squeeze the sauerkraut. Halve the yeast dough and knead again. Roll out both halves oval (35 x 25 cm). Line the fat pan and baking tray with baking paper. Place 1 dough oval on each half. Spread both doughs with the sour cream. Spread cabbage, bacon and spring onions evenly on top.
Line the fat pan and baking tray with baking paper. Place 1 dough oval on each half. Spread both doughs with the sour cream. Spread cabbage, bacon and spring onions evenly on top. Bake one after the other in the preheated oven on the lower shelf (electric oven: 250 °C/ convection oven: 225 °C/ gas: level 5) for 10-12 minutes. Serve the tarte flambée one after the other immediately warm
15 minutes waiting time