Put the chocolate, butter and vanilla essence in a heat-proof bowl.
Melt it all together in the microwave in 20 second bursts, stirring between each microwaving. It will take about 1 minute all up but be very careful not to burn the chocolate. Once melted, set it aside to cool.
In a large bowl, use a wooden spoon to stir together the cream cheese, sugar and cream until the mixture is smooth.
Add the melted chocolate and stir it through until the mixture is even.
Spoon blobs of jam into the mixture and cut it through with a spatula. Be careful not to over mix it. You want it to have a marbled effect.
Spoon the mixture into the ramekins and smooth out the top.
Refrigerate them for at least 8 hours.