Preheat oven to 350ºF (180ºC).
Coat with soft margarine or shortening a large 10 or 12-cup bundt cake pan. I use my fingers, but you can use a brush. Make sure every nook, cranny and angle is finely covered. Flour it completely, shaking off excess. Reserve.
Sift 2 cups all-purpose or cake flour with 1 teaspoon baking soda and ½ teaspoon salt. Reserve. You can sift them before in a separate bowl or have the ingredients measured and sift them directly over the batter when prompted (my choice).
In a medium bowl, melt 1 cup unsalted butter and 4.5 ounces semisweet chocolate. Do it in the microwave at 30-second intervals, stirring well after each one until just melted or on a double boiler on the stove. Add ½ cup unsweetened cocoa powder. Mix well and reserve.
In a large bowl, beat 3 large eggs with 2 cups white granulated sugar until light and creamy, about 2 or 3 minutes.
Add 1 cup sour cream, ¾ cup bourbon or whisky, 2 teaspoons pure vanilla extract and the cooled chocolate mixture. Mix at low speed until well mixed.
Add the sifted flour mixture and mix just until well combined. Pour into the prepared pan, spreading evenly.
Bake for 40 to 45 minutes, or until a cake tester or toothpick comes out clean. Let cool for 10-15 minutes on a wire rack and carefully remove onto the wire rack.
Let cool completely. At this point, you can wrap it in film and aluminum paper and freeze it for a couple of weeks. Thaw in the refrigerator and then let it get to room temperature before glazing.
Pour the glaze over and let it drip down the sides.