Line the 7-inch tart mould with the 150 g crushed digestive biscuits and 65 g melted butter, mixing until the crumbs are evenly moistened.

Press the biscuit mixture firmly across the base and up the edges of the tart mould, then refrigerate for at least 20 minutes to set.

Place the 100 g caster sugar in a heavy-bottomed saucepan and heat over medium heat until it melts into a deep golden caramel.

Spread the roasted hazelnuts on a parchment-lined baking sheet, then carefully pour the hot caramel evenly over them.

Leave the caramel-coated hazelnuts at room temperature for about 10 minutes, until the caramel is completely hard.

Break the hardened hazelnut caramel into small pieces and process them in a food processor until finely ground.

Gradually blend 2 to 3 tablespoons of neutral vegetable oil into the ground hazelnut caramel until a thick, spreadable praline forms.

Melt the 125 g dark chocolate in a heatproof bowl using short microwave bursts, stirring between bursts until smooth.

Warm the 125 ml fresh cream until steaming but not boiling, then pour it over the melted chocolate.

Whisk the chocolate and warm cream until fully emulsified into a glossy, smooth ganache.

Spread a thin, even layer of hazelnut praline over the chilled biscuit tart shell.

Pour the chocolate ganache over the praline layer and garnish the surface with reserved roasted hazelnuts.

Refrigerate the assembled tart for at least 2 hours, then slice and serve chilled.