Preheat oven to 180°C (350°F), top and bottom heat. Line a baking tray with parchment paper.
For the custard, heat the milk. Mix egg yolk, sugar, and cornstarch, add hot milk, and cook until thick. Stir in vanilla and let cool completely, covered.
Cut the berries into smaller pieces if needed.
Roll out the dough and spread the custard in a line down the center.
Add the berries on top.
Cut strips on both sides of the dough.
Fold the strips alternately over the filling to create a braided pattern.
Brush with the egg yolk-milk mixture and sprinkle with sliced almonds.
Bake for 25–30 minutes until golden.
Let cool slightly and dust with powdered sugar.
