Russian
Grate 150 g of the cold butter into 200 g of the flour with the salt and rub together quickly until the mixture looks like coarse crumbs.
Beat 1 egg with the ice water and vinegar, stir it into the flour and gather into a dough without kneading; divide into 6 pieces and chill for 30 minutes.
Roll each piece very thin on baking paper, cut out a 22 cm round, prick it with a fork and bake at 200C for 8-10 minutes until golden, baking the trimmings as well.
For the custard, whisk the remaining 2 eggs, the sugar and the remaining 25 g flour with a little of the milk, then whisk in the rest of the milk.
Cook over medium heat, stirring constantly, for 5-7 minutes until the custard boils and thickens, then cool it completely under plastic wrap.
Beat the remaining 70 g butter, softened, with the vanilla until fluffy, then beat in the cold custard a spoonful at a time.
Stack the layers with the custard cream between them and over the top and sides, cover with the crushed trimmings and refrigerate overnight before slicing.