Place slices of puff pastry next to each other and allow to defrost at room temperature for approx. 10 minutes. In the meantime, peel onions and cut into rings. Grate Comté finely. Mix crème fraîche and sour cream, season with salt and pepper. Cut the bacon slices into pieces of about 3 cm length.
Place the puff pastry on top of each other again and roll out to a thickness of about 2 mm on a floured work surface. Cut out circles (12 cm Ø). Place the remaining dough on top of each other again (do not knead), press together and roll out again. Cut out a total of 12 circles. Spread crème fraîche in the middle of the circles, spread. Fold the edges of the dough about 1 cm towards the middle. Spread onion rings and bacon slices in the middle. Sprinkle with Comté. Put the tarte flambée on 2 baking trays lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) one after the other for about 20 minutes.
Fold the edges of the dough about 1 cm towards the middle. Spread onion rings and bacon slices in the middle. Sprinkle with Comté. Put the tarte flambée on 2 baking trays lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) one after the other for about 20 minutes. Wash the chives, dab dry and cut into rings. Sprinkle the chives over the tarte flambée and serve