Preheat the oven to 125°C (approximately 250°F). Butter a large bundt pan and dust with cocoa powder.
Heat coffee and whiskey in a saucepan at over low heat.
Chop the chocolate and butter. Add to the saucepan and cook while stirring until the mixture is smooth. Remove from the heat and stir the sugar into the sauce. Let cool for 5 minutes. Transfer into a mixing bowl.
Mix the flour, baking powder, baking soda, and salt. Sift over the chocolate mixture and stir in with an electric mixer on low. Mix in the eggs and vanilla. The dough should be very liquid and smooth. Pour into the prepared baking pan.
Bake the cake for 1 1/2 hours in the oven. Check to see if the cake is done with a toothpick. Cool on a wire rack and remove from the pan. Dust with powdered sugar and serve with whipped cream.