Chocolate Key Lime Pie

Serves 6-8

300g digestive biscuits

1 tbsp cocoa powder

50g soft unsalted butter

50g dark choc chips

397g can sweetened condensed milk, chilled

4 limes, to give about 2 tbsp finely grated zest and 175ml juice

300ml double cream

1 square of best quality dark choc

Put the biscuits, cocoa, butter and choc chips into a food processor and process to a dark, damp, sandy consistency.  Tip into a 23cm x 5cm deep fluted tart tin with a loose base.  Press onto the base and up the sides.  Place in the fridge to chill while you make the filling.

Pour the condensed milk into a bowl.  Zest the limes into another bowl and reserve for decoration.  Add the juice of the limes to the condensed milk, whisking to mix.  

Pour in the double cream and whisk together - in a free standing electric mixer or with a hand held one - until thick, then spoon into the chilled biscuit crust and use the back of the spoon to finish off the top in a swirly fashion, leaving the soft filling encircled by dark crust.

Chill in the fridge for 4 hours, covered, overnight.  When you are ready to serve, unmould the pie from the tart tin, but leave it on the base.

Grate the choc to lightly dust the top of the pie, then sprinkle with lime zest.  Serve immediately, as it will become to soft if kept out of the fridge for too long.