Wash and peel the asparagus and cut off the woody ends. Cut the stems into thin slices at an angle, except for the tips. Season sour cream with salt and pepper. Grate cheese.
Unroll the dough together with the baking paper on a baking tray. Spread with sour cream. Spread asparagus, ham and cheese on top. Bake in the preheated oven (electric cooker: 225 °C/circulating air: 200 °C/gas: see manufacturer) for approx. 15 minutes. Meanwhile wash the chervil, shake dry and chop. Sprinkle the chervil over the tarte flambée.