In a large mixing bowl, stir together the Flour, Almond Meal, Cacao Powder, Confectioner's Sugar and Salt. Add the cold Butter cut into small cubes and rub it with the dry ingredients between your fingers until you get a fine crumb consistency (see note 1).
Add the lightly beaten Egg and mix it in until you get a soft dough. Gently press on the dough to flatten it, cover with plastic wrap and place in the fridge to chill for 30 minutes.
Vanilla Short Pastry
In a large mixing bowl, stir together the Flour, Almond Meal, Confectioner's Sugar and Salt. Add the cold Butter cut into small cubes and rub it with the dry ingredients between your fingers until you get a fine crumb consistency (see note 1).
Add the lightly beaten Egg and Vanilla Extract, and mix it in until you get a soft dough. Gently press on the dough to flatten it, cover with plastic wrap and place in the fridge to chill for 30 minutes.
How to assemble the Marble Cookies
Preheat your oven on 180'C and line a flat baking tray with baking paper or a baking mat.
On a lightly floured surface, roll the two doughs separately using a rolling pin (see note 2). Roughly break the doughs into small pieces, and randomly assemble the pieces to create a single dough mixing both the chocolate and vanilla pieces.
Gently roll the dough again (see note 3). to create the mixed marble pattern, adding a little bit more flour if needed.
Use a Rounded or Flutted Cookie Cutter to cut out the cookies, then transfer them over the lined baking tray (see note 4).
Bake in the oven for 10 to 15 minutes, depending on the thickness of the cookies. Leave on the tray for 10 to 15 minutes when taken out of the oven to firm up, then transfer onto a cooling rack to cool down completely.
Notes
Edit: this recipe was updated in January 2021
You can also use a Pastry Blender to cut the butter into the dry ingredients, or even the food processor.
The cookie dough will get rolled again so the thickness does not matter too much at this point, but it will be easier to assemble if not rolled too thinly.
At this point, the thickness of the cookie dough will be the thickness of your cookies. I would recommend rolling it between 2 to 4 mm (1/16 to 1/8 inch).
If the cookie dough seems to be soft at this point, place it back in the fridge for 10 to 15 minutes to firm up again. You can use a small offset spatula to move the cookies on the tray more easily.