Make the dough. Put the flour, butter, and a pinch of salt in the food processor. Mix until the mixture has a sandy texture.
Add the water and continue to mix until you have a homogeneous ball. If it doesn't work, add a little bit of water. Remove the dough from the machine, form it into a ball, and wrap it in plastic wrap. Let it rest in the fridge for at least 30 minutes.
Preheat the oven to 185 °C.
Cut the leek into fine pieces. Peel the shallot and chop it finely. Melt a knob of butter in a pan and sauté the leek and shallot.
Slice the eggplant into pieces about 1 cm thick. Sprinkle the slices with salt and brush them with olive oil. Heat a grill pan and roast the eggplant slices on one side. Season with pepper, brush with olive oil, flip them over, and roast them on the other side.
Steam the green asparagus until tender, about 4 minutes.
Beat the eggs with the cream. Season with nutmeg, pepper, and salt.
Remove the dough from the fridge. Sprinkle the work surface with flour. Roll the dough a few times with a rolling pin to soften it. Roll out the dough to about 0.5 cm thick.
Place a sheet of baking paper in a baking mold and put the dough in it. Place a second sheet of baking paper on the dough and cover the bottom with dry beans, rice, or lentils. Bake the quiche crust in the oven for about 30 minutes until it is nice and crispy.
Remove the baking mold from the oven and remove the baking paper and lentils.
Spoon the leek into the baking mold. Place the eggplant slices, green asparagus, and salmon on top. Break the goat cheese into pieces and place them on top. Pour the egg mixture over it.
Place the quiche in the oven and bake for about 20 to 25 minutes.
Meanwhile, prepare the salad. Peel the onion and cut it into strips. Peel the kohlrabi and grate it finely. Remove the core from the apple and cut it into thin slices. Mix the mizuna with the onion, kohlrabi, and apple.