For the dough, put flour, baking powder, salt, butter in flakes and 3 tablespoons of cold water in a mixing bowl and knead with the dough hooks of the hand mixer. Then work into a smooth dough with your hands.
Roll out to a circle (approx. 23 cm Ø) on a floured work surface. Place in a greased, flour-spread tart mould (20 cm Ø) with lift-off base, press lightly, prick several times with a fork and chill for approx. 45 minutes.
In the meantime clean, wash and dice the carrots. Pour into boiling salted water, bring to the boil and cook over medium heat for about 5 minutes. Drain, quench, drain well and let cool off. In the meantime mix sour cream and eggs.
Season to taste with salt, pepper and nutmeg. Spread the carrots evenly on the base. Pour over the mixture. Bake on the lowest shelf in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 45 minutes.
Take it out of the oven. Carefully remove from the mould and serve garnished with chervil.