Roll the puff pastry to a 3 mm thickness and cut four circles slightly larger than the tart rings.

Line the four perforated tart rings with the puff pastry and prick each base with a fork.

Freeze the lined pastry shells until firm, for about 15 minutes.

Bake the pastry shells on a baking sheet at 175°C for 30 minutes until crisp and golden.

Split the vanilla bean and scrape its seeds into a mixing bowl with the 60 g egg yolk and 35 g brown sugar.

Whisk the egg yolk, brown sugar, and vanilla seeds until the mixture is smooth.

Heat the 250 g heavy cream and 25 g salted butter in a saucepan until just boiling.

Pour the hot cream mixture gradually over the egg yolk mixture and whisk continuously.

Pour the custard evenly into the four baked pastry shells.

Bake the filled shells at 100°C for 40 minutes, until the custard is gently set.

Cool the crème brûlée completely, then sprinkle 10 g demerara sugar over each surface.

Caramelize the demerara sugar with a kitchen torch until it bubbles and forms a crisp amber crust.