For the vegetable quiche, first heap the flour on the work surface for the shortcrust pastry, put the soft butter in the middle, add the egg yolks, a little salt and a splash of water. Knead everything into a smooth dough, wrap it in cling film and let it rest in the fridge for about half an hour.
Roll out the dough thinly on a floured work surface, pour it into a greased springform pan, cover with aluminum foil and sprinkle lentils on top. Blind pre-bake the dough in the oven at 180 °C for 15 minutes.
Clean vegetables, cut into 1 cm pieces and cook in salted water until al dente, remove and drain well. Sauté the onion in a frying pan with butter until soft. Mix the vegetables with the cheese, the onion cubes and the chives. Spread everything on the pre-baked dough (first take down the aluminum foil with the lentils). Cooked vegetables from the previous day are also suitable.
Mix whipped cream, eggs and 10 g flour, season with salt, pepper and nutmeg and pour over the vegetables, bake at 180 °C for about 20 minutes.
Serve the vegetable quiche lukewarm.