Bring the milk to a boil in a small saucepan over medium heat.

In a large heatproof bowl, whisk together the egg yolks, sugar, and vanilla bean paste with a balloon whisk until thick and pale. Whisk the milk into the egg mixture gradually. Pour the mixture into the pan. Cook, stirring constantly with a wooden spoon, for 5 minutes, or until the mixture thickens and coats the back of the spoon. Strain into a large heatproof bowl using a fine sieve.

Fill a small heatproof bowl halfway with cold water. Sprinkle with gelatine. Place the bowl in a saucepan half-filled with hot water, working quickly. Whisk with a fork until the gelatine dissolves. Incorporate the gelatine mixture into the custard mixture. Refrigerate for 30 minutes, stirring frequently, or until the mixture begins to thicken (do not allow it to set).

In a mixing bowl, whip the cream with an electric mixer until soft peaks form. Fold the cream into the custard mixture with a large metal spoon. In a small bowl, combine the coffee and boiling water and stir until the coffee dissolves. 250ml (1 cup) of the custard mixture should be added to the coffee mixture. Stir until thoroughly combined.

Divide the remaining custard mixture among six 200ml dariole molds. Fill a piping bag fitted with a 5mm round nozzle with the coffee custard. Squeeze a small amount of coffee custard into the center of the vanilla custards with the piping nozzle. Refrigerate for 6 hours or overnight until set.

To make the mocha sauce, in a small saucepan over low heat, combine the sugar, water, cocoa, and coffee until the sugar dissolves. Bring to a boil and continue to cook for 5 minutes, or until the syrup thickens slightly. Allow to cool completely.

Dip the molds in hot water for 10 seconds before transferring to serving dishes. Drizzle with mocha sauce and garnish with chocolate curls.