How to make
Put the water to boil in a suitable container. Add the butter, sugar and salt. Once it reaches boiling point, remove from the stove, pour in the flour and stir vigorously with a wooden spoon. Return the container to the stove and cook until you get a smooth dough. Leave it to cool.
Clean the peppers of their seeds, the onion of its peels and cut them into suitable pieces. Saute the vegetables in heated oil until softened. Add the cleaned and chopped mushrooms. The stuffing is ready once the ingredients get a slight brown crisp. Add the parmesan, stir and cool.
Lay out baking paper at the bottom of a suitable oven dish. Smear the walls with butter. Spread out a part of the dough, covering the bottom and walls. Bake in a preheated oven for 10-15 min. without opening it.
Take the oven dish out, pour in the stuffing, pour in the whisked egg, season with the black and white pepper. Spray the rest of the dough along the edges of the pie. Bake until golden. Sprinkle with grated cheese at the end.