- Place chocolate in a heatproof bowl set over a saucepan of barely simmering water. Stir occasionally with a metal spoon until melted. Remove from heat, slowly pour oil into bowl with chocolate, stirring constantly until combined.
- Meanwhile, whisk cream in a bowl to soft peaks. Gradually pour in chocolate mixture, whisking to combine. Serve immediately.
- Place water and sugar in a small saucepan and bring to the boil, swirling pan occasionally to dissolve sugar. Cook for about 5 minutes until the temperature reaches 110°C.
- Meanwhile, place chocolate in a heatproof bowl set over a saucepan of barely simmering water. Stir occasionally with a metal spoon until melted.
- Meanwhile, using an electric mixer fitted with a whisk attachment, whisk cream to soft peaks. Set aside.
- Whisk yolks and eggs on high speed for 4 minutes until light and fluffy. With the motor running, slowly pour in the hot sugar syrup, whisking until the mixture is cool.
- Fold egg mixture into chocolate until combined, then fold in half the cream until combined, followed by the remaining cream. Serve immediately.
- Melt chocolate in a heatproof bowl in a microwave on medium heat for 1 minute. Stir, then return to microwave in 30 seconds increments until chocolate has completely melted, stirring well each time.
- Place milk in a small saucepan over medium heat, and bring to the boil. Gently whisk milk into chocolate until just combined. Set aside to cool slightly. Gently whisk in egg yolks until just combined.
- Meanwhile, using an electric mixer fitted with a whisk attachment, beat egg whites to soft peaks. Slowly add sugar, beating until stiff and glossy.
- Fold in one-third of the meringue into chocolate mixture until just combined, then fold in the remaining meringue until combined.
- Pour mousse into serving bowl and refrigerate for at least 1 hour before serving.