A layer of chocolate is stuck on a butter cookie, and that's a Chocolate Butter Cookie. Both are rectangular, and the chocolate butter cookie is a sandwiched cookie.
Make a smooth paste by combining the soft butter and sugar in a bowl.
Add the vanilla to the butter sugar mix. If you are using vanilla bean, slit open the vanilla bean and scratch out the tiny black seeds. If you are using vanilla bean paste, extract or sugar, just add the vanilla flavoring to the preliminary dough.
First, add the flour and a small amount of water to the mixing bowl, followed by a thorough mixing process to produce a smooth dough. Add more of the water if the dough is too dry, but be carefully with adding water because if your dough is too sticky, you will have to add a small quantity of flour to adjust the consistency. The dough shouldn't stick, and it shouldn't crumble either. The dough should hold together without separating.
Wrap the dough into clean wrap and place into the fridge. Cool for 1 hour. *See Notes
Just before rolling out the dough, preheat your oven to 320 Fahrenheit (160 °C).
Roll out the dough with enough flour so that it doesn't stick. The dough should be about 0.1 inch or 3 mm thick.
Cut out your biscuits with a cookie cutter and place on a baking parchment, which you prepared ahead, over a baking sheet. Finnish up the whole dough by rolling and cutting out the cookies.
Bake the cookies at 320 Fahrenheit (160 °C) for about 15 minutes, or until lightly golden. Leave your cookies to cool after baking.
Melt your chocolate in a Bain Marie (pot with water and another pot over that containing the chocolate) so that the chocolate doesn't burn.
Pour the chocolate into the mold and let cool for 20 minutes.
Once your chocolate has cooled and hardened, add some melted chocolate onto the biscuit side to glue it on and stick the molded chocolate onto the shortbread cookie.
Store the biscuits in a cookie tin box or plastic container (please see storing instructions in post for your climate).
Notes
For the Vanilla choose either vanilla bean, vanilla bean paste, vanilla extract or vanilla sugar. For the base recipe, extract from one vanilla bean, or use about ½ teaspoon vanilla bean paste, or a few drops of vanilla extract or about 1 teaspoon of vanilla sugar. You can also adjust it to your liking.
You can use Dark Chocolate and/or White Chocolate and/or Milk Chocolate
The quantity of water that you have to add to your dough highly depends on your flour quality and your environment. For example, I found that a humid climate would require less water and a dry climate somehow results is much drier flour.
The dough needs to be cooled for 1 hour so that it hardens in the cool environment. Your shortbread dough will only roll out if you have it cooled first. Keep in mind, the more you touch your dough with your warm fingers, the more the butter will melt again, and that makes the rolling and cutting out part more challenging.