Preheat oven to 200°C. Lightly coat a 32 cm x 23 cm cake tin with cooking spray and line with baking paper.To make the pastry, bring the water and butter to a boil in a medium-sized saucepan. When the butter is completely melted, sift in all the flour. Stir over a low heat until the dough comes off the sides of the pan, then leave to cool for 10 minutes.Stir in 5 whole eggs, one at a time to that mixture, beating well after each. The batter should be smooth and shiny and stick to your spoon with ease. Divide it into two batches.Spread one half of the mixture into the pan but do NOT smooth it out. Bake for 25-30 minutes until golden in colour. Do not open the oven door during baking. Remove the pastry from the pan and cool on a wire rack. Remove the pan from the oven and place the baked pastry on a wire rack to cool. Repeat the process with the other half of the pastry and also remove to cool.To make the cream filling, in a medium saucepan, boil 2 cups of milk with the sugar and vanilla. While the mixture is cooking, blend the remaining cup of milk with all 4 eggs yolks, 1 whole egg, potato starch and flour. Once blended, slowly add it to the boiling milk, stirring constantly.Cook for 2 minutes, then set aside to cool to room temperature.Ensure the filling is completely cooled before beating in the softened butter.Lay your first pastry sheet on a workbench, spread over the cream filling, then place the second pastry sheet on top. Refrigerate.To serve, dust with icing sugar.This recipe and image are from .