To make the cream, beat the mascarpone cream, sugar, and vanilla until smooth. Add the heavy cream and beat until you get soft peaks.
To assemble the cake, place one cake layer on cake stand, spoon half cup of jam on olive oil cake and spread. Then spread or pipe half the mascarpone cream on top, add fresh blackberries (save some for decorating) Place second cake layer on top and repeat with the same steps as above. Cake can be stored in fridge covered for up to three days.