Beat the butter and sugar together until ligiht and fluffy
1 cup Butter, ½ cup White Sugar
Add in the cocoa and vanilla and beat until combined
½ cup Cocoa Powder, 1 teaspoon Vanilla Extract
Add in the flour and salt and mix everything together until everything is combined and a dough starts to form
1 ¾ cups All Purpose Flour, 1 teaspoon Salt
Use your hands to bring the dough together into a ball and knead very lightly. Wrap in clingfilm and put in the fridge to chill for 1 hour
Once the dough has chilled, preheat the oven to 350°F/180°C and line a cookie sheet with parchment paper
Flour your work surface and roll out dough very gently to about ¼ inch thick
Cut out rounds and place them on the cookie sheet
Bake for 8-12 minutes. The cookies will have a sort of shiny look to them as they bake, as soon as the shine disappears, the cookies are ready. They will still be very soft to touch, they will continue to bake on the tray as they cool
Remove from the oven but leave the cookies on the tray until completely cooled
Make the Ganache
Chop the chocolate into small chunks and place in a bowl. Set aside
300 g Semi-sweet Chocolate
Heat the cream in a saucepan over medium-low heat. Don't let it boil, you want to heat it just until tiny bubbles start to form, then remove it from the heat immediately
200 g Whipping Cream
Pour the cream over the chocolate and let it start to melt. Stir constantly until all the chocolate has melted and the ganache is shiny and smooth. Let cool.
Assemble the Sandwich Cookies
Make sure the cookies and ganache have both completely cooled before assembling. Ganache should be soft but solid (.i.e. not liquid)
If you are whipping the ganache, do it right before assembling the cookies. Use a stand or hand mixer and whip it on high until the desired fluffiness is reached. I beat mine for about two minutes.
Line up your cookies with cookie twins that are similar in shape and size
Pipe or spread ganache onto one of the cookies and sandwich together with the other. Enjoy!
Notes
If the ganache is too soft when trying to eat, put them in the fridge for 10 mins before serving and it will firm up perfectly.