Preheat oven to 350 degrees Fahrenheit.

Process the flour, filberts, sugar, and margarine or butter in a food processor until the mixture resembles fine bread crumbs. While the motor is running, add enough ice water to form a smooth dough and process until just combined. Do not overprocess. Knead the dough lightly, wrap in plastic wrap and refrigerate for 30 minutes.

Roll out the pastry on a lightly floured surface or between sheets of non-stick parchment paper until 1/8 inch thick and line a 10-inch (26-centimeter) tart tin with the dough.

Place a piece of parchment paper over the pastry and fill with baking weights or uncooked rice or beans. Bake for 10 minutes, then remove the weights and parchment paper and bake for a further 10 minutes or until the pastry is golden. Remove from oven.

Reduce oven temperature to 300 degrees Fahrenheit.

Place the egg yolks and sugar in a bowl and whisk until the sugar is dissolved. Place the soy milk and dessert whip or coconut milk in a double boiler. Bring to just under a boil and remove from heat.

Add the chocolate and stir until smooth. Pour chocolate mixture over the egg yolk mixture, stirring constantly as you pour, until combined.

Pour filling into the tart shell, almost to the top, and bake for 17–20 minutes or until just set.

Cool completely, then serve in wedges.