Instant Chocolate Mousse

Put the marshmallows, butter, chocolate and water in a heavy-based pan.

Put the saucepan on the hob, over heat, though keep fairly gentle, to melt the contents, stirring every now and again.

Remove from heat.

Meanwhile, whip the cream with the vanilla extract until thick, and then fold into the cooling chocolate mixture until you have a smooth cohesive mixture.

Chill until want to eat.