Cream the butter with the icing sugar and the ground almond.
Add the egg and mix until smooth.
Add the flour and mix until the flour is blended in but don't overmix.
Pat the dough into a disk, wrap and refrigerate for at least 1 hour.
Place a 9-inch (23 cm) tart pan with removable bottom on a sheet pan. Set aside.
Using a rolling pin, roll out the chilled dough on a lightly floured surface until it's 11.5–12 inches (29.2–30.5 cm) in diameter. Work fast so the dough doesn't get too warm. The dough will become more delicate the warmer it gets.
Fold the dough in half and carefully transfer to the tart pan to line it with the dough. If the dough breaks, don't worry. You can just press any cracks or breaks back together. Trim the edges using a knife or your rolling pin.
Dock the pastry using a fork to poke holes over the entire surface. Chill the unbaked shell for 1 hour.
Preheat the oven to 350 °F (175 °C). Bake the tart shell for 20 to 25 minutes, until the edges are golden brown and the pastry looks dry and baked through. Keep an eye on the tart shell and be sure to press down any areas that may bubble up during baking before the crust sets and dries.
Place the milk in a medium saucepan with half the sugar. Set it to heat on the stove on medium–high.
Meanwhile, in a large bowl, whisk the eggs with the sugar untiil light and fluffy and pale in colour. Whisk in the cornstarch until the mixture looks thick and creamy.
When the milk is just about to boil, take the pan off the heat and pour the milk over the whipped yolk mixture. Whisk everything together really well to temper the eggs.
Transfer the mixture back to the saucepan and heat on medium heat until the pastry cream comes to a boil, whisking constantly.
Boil the pastry cream for 3 minutes.
Take the pan off the heat and add the butter, a piece at a time, whisking constantly. You can decide at this point if you want to strain it or not.
Transfer the cooked pastry cream to a bowl, cover in plastic wrap, and chill for at least 1 hour.
Assembly and finishing
When the baked tart shell has cooled completely and the pastry cream is cold, you are ready to assemble the tart.
Place the unmoulded tart shell on your serving plate. Brush the inside of the tart shell with the melted white chocolate to coat the entire surface and protect it from moisture.
Place the tart shell in the fridge for 5 minutes to set the chocolate if it's warm in your kitchen.
Take the pastry cream out of the fridge, unwrap it, then using a whisk, whip the pastry cream until it is smooth and creamy. This will take a few minutes because it will be quite firm but it will smooth out the more you work it.
Spread the pastry cream in the tart shell and smooth it out so that it's even.
Top the pastry cream with lots of fresh berries and sliced fruits, arranging them in a pattern or haphazardly, as you like. Cover the pastry cream completely with fruit so that none is exposed.
Store the fruit tart in the refrigerator until you are ready to serve it.