This year I've tried two different biscuit bases: oreo cookies and custard creams. I've also chosen four flavours: vanilla and mint for the oreos and raspberry liquor and orange for the custard creams.
I put in two capfuls of the essense in the oreo truffles but was worried it wasn't strong enough so tried four for the custard creams.
These are really excellent truffles to make because the centres don't melt as you coat them in chocolate. The cookies also give a very firm, strong filling.