Preheat the oven to 325°F and line a 9 inch springform pan with parchment paper. In a microwave safe bowl combine butter and chocolate. Place in the microwave and set at 50 seconds, then stir. Add more time, 10 seconds at a time until completely melted. Cool.Separate the egg whites from the yolks, placing the yolks in a separate bowl and the egg whites in the bowl of a stand mixer with a whisk attachment. Whisk the egg whites and add granulated sugar as it’s whisking. Continue beating on high until medium stiff peaks form.Add the yolks into the chocolate and butter mixture and whisk. Add the vanilla, salt, coffee, bourbon and cocoa powder. Whisk again. Fold in the whipped egg whites into the chocolate mixture until combined. Mix until combined. Do not over mix. Spoon the batter into the prepared pan. Use a rubber spatula to spread.Bake at 325°F for 45 to 50 minutes until the edges of the cake start to pull away from the sides of the pan. Cool completely then dust with confectioners sugar.
