Preheat oven to 325°F then coat bundt pan with butter and dust with flour.
Melt dark chocolate and set aside. Put 1 cup of water on to boil.
Mix instant espresso powder, cocoa powder, boiling water, bourbon and salt in cup. Add enough boiling water to make all ingredients fill to the 1 cup marker on the measuring cup.
Place softened butter in bowl and beat until fluffly. Add sugar and eggs then mix. Add baking powder and vanilla and mix. Once this is mixed well, add the melted chocolate and mix.
Alternate adding bourbon espresso mixture and the all purpose flour into the mixing bowl and mix on lowest speed between each addition.
Pour mixture into bundt pan and bake about an hour and 10 minutes or until a tester comes out clean from the middle of the cake.
Allow cake to cool and then sprinkle bourbon over the cake.