Preheat the oven to 180C and mix the crushed biscuits and the melted butter in a bowl.
Empty this into a 23cm - 26cm loose-bottomed tart tin and gently press the mixture into the sides. Place the tart onto a baking tray and bake blind for 8 minutes.
Peel the pears and cut them in half. In a medium, pot heat the verjuice, sugar, and vanilla. cook the pears for 8 minutes. Remove from the liquid, and set aside to cool.
For the frangipane, mix the butter and castor sugar in a food processor and add each egg while the motor is still running. Add the cocoa and almonds and blend well.
Spoon the frangipane into the tart case. Remove the cores from the pears and slice these (in a fan shape), and arrange them on the frangipane. Scatter over the sliced almonds.
Bake for 30 - 35 minutes until the frangipane is cooked through (bake on a tray in case any butter leaks out)