Blend the dry ingredients and butter in a food processor or by hand. Mix in the egg and water to make a soft dough, try not to over mix. Wrap in cling film and chill for an hour before using.

Roll out the dough, and line a 20cm tart tin. Bake the pastry blind, by placing a piece of baking paper over the pastry and filling with rice or ceramic pastry beads.

Bake the pastry at 180°C for 10 mins. Remove the paper and rice/pastry beads, and cook for another few minutes until just coloured. Remove the pastry from the oven.

Mix all the filling ingredients together in a bowl, reserving the walnut halves to place on top.

Re-set the oven heat to 160°C. Fill the cooked pastry shell with the kumara and walnut filling, and top with the walnut halves. Place carefully in the oven and bake until set, around 10-15 mins.

Serve at room temperature with a little whipped cream and a sprinkle of icing sugar.