In a bowl, combine the flour, sugar, and salt.

Grate the butter directly into the bowl using the large holes of a box grater. Work the flour into the butter using a pastry cutter or by hand until the mixture resembles a coarse meal.

In another bowl, combine the cold egg, ice-cold water, and vinegar. Whisk with a fork to break up the egg.

Pour into the center of the dry ingredients in several additions, mixing with a fork between each one. Finish bringing the dough together with your hands but don't knead it, just press until a dough ball forms. Shape it into a log, split into 9 even pieces, and roll into balls. Place on a large plate, cover with plastic wrap, and freeze until very cold but still pliable. You can also refrigerate the dough overnight.

Meanwhile, preheat the oven to 200C (400F) and prepare 4 pieces of parchment paper and a baking sheet.

When the dough has chilled, take one ball at a time out of the freezer. Dust the rolling surface, the pin, and the dough ball with flour. I recommend rolling the dough directly on parchment paper. Roll it out thinly into a roughly 9½–10 inch (24–25 cm) circle and bake as is. You will cut out the 7-inch disk after baking.

Prick the dough all over with a fork and bake for 10-12 minutes or until golden. If your oven has hot spots, rotate the baking sheet once one side turns golden brown.

Remove from the oven and place the parchment paper with the baked pastry on a flat surface. Let it rest for 1 minute, then cut out a 7-inch (18cm) round cake layer using a metal cake ring and a small knife, or use a 7-inch paper stencil prepared in advance. Place the trimmings on a separate plate. Repeat with the rest of the dough.

In a saucepan, combine the sugar, cornstarch, and salt.

Add the egg yolks and vanilla extract and mix well.

Pour in the milk. Cook over medium heat, whisking constantly, until the mixture thickens to a pudding-like consistency, about 5 minutes. Lower the heat and cook for a further 1-2 minutes, still whisking. Remove from the heat and add the butter, mixing until fully incorporated.

Pour into a clean bowl, cover with plastic wrap pressed directly onto the surface, and place in the freezer for 30 minutes to 1 hour until cold. Alternatively, leave it in the saucepan, cover the same way, and refrigerate overnight.

Once the cake layers are at room temperature and the pastry cream is cold, whip the heavy cream with the powdered sugar to medium peaks.

Whip the cold pastry cream until smooth and glossy, then fold in the whipped cream with a rubber spatula until fully combined.

Spread a small amount of cream onto the serving plate to anchor the cake. Place the first cake layer on top and press gently.

Add around 85g (approximately ⅓ cup but I recommend using kitchen scale to make sure you will have enough cream to crumb coat the cake) of cream on top and spread evenly with an offset spatula. Place the next cake layer on top and press gently. Continue until all cake layers are used.

Use the remaining cream to make a crumb coat and fill any gaps on the sides.

Place the pastry trimmings in a food processor and pulse until sandy. Cover the top and sides of the cake with the crumbs, then place in an airtight cake box or cover with plastic wrap and refrigerate for a minimum of 6 hours, or preferably overnight, to allow the cake layers to soften. Decorate as desired and serve.