Altered ingredient amounts.
Instead of pastry base try chocolate biscuit base.
200g of chocolate digestives (milk or dark)
110 g of melted butter (recipes always say unsalted but personally I like the slightly salted taste with chocolate especially when having with a tart flavour)
Break biscuits into crumb (in blender or in a plastic bag and bash with rolling pin)
add butter and press into bottem and up the sides of 23cm tart tin, bake for 8 mins in oven at 180oC gas mark 4, add filling as in recipe.
A nice alternative for chocolate lovers - 20 Nov 2010