Think of this as a grown-up version of a hedgehog slice. Super-short orange-scented biscuit adds crunch to a whipped truffle ganache, while candied orange and a slug of orange liqueur bring the luxe factor. It's rich, dark and not for the faint-hearted. For an extra flourish, we've scattered the slice here with diced candied orange and chocolate biscuit balls (Callebaut Crispearls, available from Chefs' Warehouse), but it's still great simply dusted with cocoa. Start this recipe a day ahead to set the slice. The recipe makes about 30 pieces.