Divide the puff pastry into 2 equal parts and bake them in a lightly greased baking dish separately. For the cream, heat the milk and sugar to boiling, set aside about 1 1/5 cups (300 ml).
Separately, beat the egg yolks with the cooled milk, butter and flour. Pour in the hot milk in small batches to the yolks.
Temper the 2 mixtures together and finally add the egg mix to the boiling milk while stirring. When the cream has thickened, flavor with the vanilla and remove from the heat.
Cover it with foil and let it cool completely. Beat the egg whites with a pinch of salt until you get a fluffy snow. Gently mix them with the already cooled cream. Pour the whole mixture on one layer in a baking dish and cover well with the others. Sprinkle with powdered sugar.
Leave the cream pita to sit for about 2 hours.