Place coarsely chopped chocolate in a medium sized heat safe bowl and set aside.
In a small saucepan over medium heat bring the heavy cream to a boil. You just want to get it to the point of a boil and then remove it from the heat as soon as it does.
Pour the scalded heavy cream over the chocolate and let stand for 2-3 minutes undisturbed until chocolate has softened.
Slowly whisk the mixture until smooth and add the room temperature butter. Whisk until butter is melted and incorporated.
Either add ganache to pastry bag or place plastic wrap directly on the surface of the ganache and allow to cool at room temperature for 2-4 hours.
Match cookie pairs according to size. Put the first cookie face down. Pipe on some ganache, making it thicker on one side. Place top cookie on ganache and press down on only one side to give the illusion of an open mouth.
Use additional ganache on top to make your eyes stick.