In a small pastry bowl, beat the egg with sugar and corn starch; set aside. Meanwhile, heat milk and whisk in nescafe and boil. Temper the egg mixture with half of the hot milk; transfer mixture back into the saucepan. Bring to boil and cook for 2 minutes; whisking constantly. Turn heat off and whisk in cocoa powder, add the chopped dark chocolate or disks – allow chocolate to melt and whisk well until smooth. Transfer chocolate custard onto a dish lined with plastic wrap, cover custard with plastic wrap in contact. Cool to room temperature and refrigerate completely.

Grease and flour the cake pan. In a stand mixer fitted with the paddle attachment, combine flour, cocoa powder, salt, sugar, baking powder and baking soda together. Add the room temperature butter and sand for a minute or so. Add vanilla and eggs and mix to combine on low. Wrap up pastry and chill a couple of hours or until it has completely hardened.

Note: The crust and custard can be both made a day ahead.

Egg-Wash: Beat an egg with a pinch of salt. Milk or heavy cream can be used instead of egg-wash.

Beat the chilled chocolate custard until smooth and set aside. On a floured work surface, divide chilled chocolate crust into 2 equal portions. Roll out bottom into a generous 1/4’’ (6 to 7mm) thick disk. Drape the pastry over the prepared pan. Using your fingers, press dough into place in pan. Fill evenly with the chocolate custard. Roll out the second disk into the same thickness and place over the pan. With the rolling pin, trim off excess dough and remove excess flour. With a pastry brush, paint cake with a light, even coat of egg wash and design strips using the back of a fork. Chill cake an hour before baking or refrigerate for up to 3 days. It can be frozen for weeks as well (allow cake to thaw overnight in the refrigerator before baking).

In a preheated oven, bake at 350ºF (180ºC) for 35 to 40 min. Cool to room temperature and chill over night before unmolding. The cake can be kept refrigerated for up to 3 days. To unmold the gâteau Basque, loosen edges with the tip of a paring knife. Place a plater on top of the cake and flip. Blow torch bottom for a few sec (or use the flame from the stove) and remove the pan. Place another plater or large plate on the top of the bottom cake and flip again (serve designs side up). Divide cake into 2 halves, then each half into 6 servings. Warm up gâteau Basque before serving if desired and pair with your favorite sorbet such as red fruit, mango, clementine, lemon, pistachio, vanilla, cherry etc.. Enjoy!.