Preheat oven to 325 degrees. Butter or spray with cooking spray a 10-inch bundt pan, and dust with 3 Tbsp cocoa powder, shaking out the excess. Set aside.
In a medium saucepan over medium heat, add whiskey, coffee, butter and remaining cup of cocoa powder. Heat , whisking occasionally, until butter is melted. Remove from heat. Add sugar and whisk until dissolved, about 1 minute. Transfer to a large bowl and cool 5 minutes.
While mixture cools, whisk together flour, baking soda and salt in a bowl. Whisk together eggs and vanilla in another small bowl.
Whisk egg mixture into cooled chocolate mixture. Then add flour mixture and whisk until just combined (batter will be thin and bubbly). Pour batter into prepared bundt pan and tap to remove air bubbles.
Bake for 45-50 minutes until a toothpick in the center of the cake comes out clean. Cool cake completely in the bundt pan on a rack for about 1-2 hours. Loosen cake with dinner knife and turn out onto a rack or plate.
Once completely cool, sprinkle icing sugar over the top with a small sifter, and/or serve with whipped cream on the side.
Enjoy!