To make the pastry put butter, icing sugar and flour into a mixing bowl and rub the butter into the flour and sugar using your index and middle finger against your thumb to make breadcrumbs. Alternatively put the ingredients into your food processor and process to breadcrumbs.
Add the egg yolk and water and process to a dough.
Put onto a floured surface (if the dough is too soft put it in the fridge for 30 minutes) and roll out the dough to a 3 mm thickness.
Line the tart ring, making sure you press well into the corners.
Place in the fridge for one hour.
Place greaseproof paper into the pastry base and fill it with rice or baking beans.
Bake the pastry in the oven for 20 minutes, remove the paper and place it back into the oven for another 5 minutes. Allow to cool.
Mix the prunes and walnuts in a bowl and pour them into the base of the tart.
In the same bowl cream the butter and sugar until pale.
Add the ground almonds, flour, eggs, honey and orange zest and mix well, then fold in the cream.
Pour the mixture into the tart and bake in a preheated oven at 160°C for approx. 40 minutes.