Bring the sugar, scraped vanilla bean, and water to a boil in a saucepan.

Remove from the heat.

Set aside.

For extra fragrance, add rose water, orange blossom water, or a liqueur such as Cointreau or Disaronno.

Preheat the oven to 180 °C.

Using a paring knife, cut a 2.5 cm-wide, 2.5 cm-deep hole in the center of each brioche without cutting all the way through.

Dip the brioches in the vanilla syrup for 5 seconds to soak them.

Place the soaked brioches on a wire rack to drain off any excess syrup.

Fill each brioche with pistachio paste.

Bake for 12-15 minutes.

Remove from the oven.

Let cool completely on a wire rack.

Whip the heavy cream with the vanilla until stiff peaks form.

Pipe the whipped cream onto the brioches in a spiral using a star tip.

Sprinkle with crushed pistachios before serving.