2 1/2 sticks butter, slightly softened
1 1/4 cups sugar
1 1/2 tsp vanilla extract
3 cups flour
1/2 tsp salt
1/4 tsp baking soda
2 tbsp strong coffee, cooled
4 tbsp unsweetened cocoa powder
4 oz bittersweet chocolate, melted and still warm
Cream butter using an electric mixer until smooth, about 2 minutes.
Mix in sugar and beat for an additional 2 minutes. Add in egg and vanilla and mix until well combined.
Sift in flour, salt, and baking soda and mix with the creamed until just combined.
Take 2 cups from the dough and set aside.
Add in cooled coffee and cocoa powder to remaining dough. Mix in melted chocolate until well combined.
Divide both dough into three equal pieces, so as to have 3 chocolate and 3 vanilla.
Shape each piece into a 5x5 square on wax or parchment paper, top with another piece of wax or parchment and refrigerate for 30 minutes.
Roll each square into a 7x7 square and refrigerate for 15 minutes.