Sift the flour into a bowl, quickly knead with 120 g of butter cubes, salt, 1 egg and 1 - 2 tablespoons of water using the dough hook of a hand mixer. Wrapped in foil, leave to rest in the refrigerator for at least 1 hour.
Peel and quarter the kohlrabi and cut into ½ cm thick slices. Cover and cook with 300 ml water, 50 g butter, salt and nutmeg for 6 - 8 minutes until soft. Drain and collect 100 ml kohlrabi water. Drain the kohlrabi well and let cool.
Mix the kohlrabi water with crème fraîche, cream, remaining egg, egg yolk, salt, pepper, nutmeg and parsley well with a cutting stick.
Grease the bottom of a tart pan (26cm) well or cover with baking paper. Roll out the dough on a floured work surface, it should be slightly larger than the shape. Line the mold with the dough, press down firmly, only lightly cut off the protruding edge. Prick the base several times with a fork, chill for 30 minutes.
Roast the sunflower seeds in a pan without fat until light brown, distribute with the kohlrabi in the dish.
Pour on the eggs and cream. Bake in the preheated oven at 200 ° C on the lowest rack for 45 minutes.
Mix the mustards with lemon juice and oil well with a cutting stick. Stir in the dill and chives, season with salt, pepper and a little sugar if necessary. Serve the sauce with the quiche.