There are many variations on this very simple desert, but here's my take on it. Sounds and looks difficult and time consuming but it really isn't. But don't tell anyone! Cooking time is actually cooling time to set.
Place pastry on flat tray and bake for 15 minutes at 350.
To make cream (filling), mix egg yolks with flour and some cold milk. Boil milk with vanilla extract, sugar and orange zest. pour milk slowly to egg mixture, constantly mixing. Simmer on very low heat for 10 minutes constantly mixing. Remove from heat and add dissolved gelatin in some cold water. Mix well. Let the filling cool off.
Mix vanilla sugar with some cream and add to filling while still warm. Spread filling over baked pastry, top with whipped cream and cover with second baked pastry sheet. Place into refrigerator and cut vanilla slices just before serving. Sprinkle with powdered sugar and serve with fresh fruit in season.