Prepare the dough. Mix flour and salt and put in the freezer for 30 minutes. Put flour and butter in the processor bowl, mix into crumbs in a pulse mode. Add cheese and egg, mix until the mass begins to collect in a ball. Immediately turn off the processor, transfer the dough to the mat, quickly knead with cold hands, press down to make a disc, wrap in plastic wrap, and put in the refrigerator for at least 1 hour.
Preheat oven to 180 degrees. Roll out the dough into a thin layer, transfer it to a mold with a diameter of 20 cm, gently press it against the walls. Chop the bottom with a fork often. Place baking parchment on top of the dough and sprinkle special ceramic balls, dry peas or beans on top.
Bake for 20 minutes. Then remove the parchment and balls, bake for another 7-10 minutes until the dough turns golden. Meanwhile, prepare the filling. Sprinkle the onions with salt and pepper and fry until soft. Add peas, zest and dill, stir and set aside.
Beat eggs lightly, add Parmesan, stir. Heat the cream and milk to a near boil. While stirring constantly, slowly pour into the egg-cheese mixture. Add vegetables and fish pieces, stir.
Pour the filling over the base, place the quiche on the middle shelf of the oven. Immediately reduce the temperature to 160 degrees. Bake for 30-40 minutes. The filling should grab, but shake slightly in the middle. If the filling is ready, and the surface looks too pale, you can raise the quiche higher and hold it under the grill at 200 degrees for several minutes.
Leave in the mold for 15 minutes, then gently remove and cool to room temperature. Keep refrigerated.