Place the butter in the freezer for 20 minutes. Wash and break the egg, beat it. Sift the flour thoroughly and more than once so that it is saturated with oxygen. Line a baking tray with baking paper. Preheat the oven to 200 degrees.
Prepare the dough. Mix water with salt and lemon juice and stir. Sprinkle a mound of flour onto the surface. Make a hole in the slide. Pour water into it and start kneading the dough. Add water as needed to keep the dough from being sticky. Divide the butter into 6 parts, roll out the dough into a thin layer. Grate 1 part of the butter and spread over the dough. Fold it, roll it out. Do the same 5 more times. Let the dough cool for 90 minutes.
Prepare the vol-au-vents. Sprinkle the table with flour. Roll out the dough into a thin layer. Using a mold or glass, cut out circles, cut half into rings. Form scraps into a ball, roll out and repeat. Place the circles on a baking sheet and place the rings on top. To secure the bottom and sides, brush the workpiece with beaten egg. Keep a distance of at least 2 cm between them, as they will increase. Place the vol-au-vents in a hot oven. Bake for 15-20 minutes.
Serve the vol-au-vents with the filling of your choice. Any filling is suitable - pates, salads, snacks. Remember to only put the filling in the baked pans and avoid liquid fillings. From them, the vol-au-vents will instantly become soggy and lose their taste and appearance.