Preheat oven to 350 degrees. Coat your heritage bundt pan with non-stick cooking spray. Dust the pan with about 2 T. unsweetened cocoa powder. Tap out any excess cocoa powder.
In a microwave-safe medium bowl, add in the water and butter. Microwave for 2 ½ minutes.
Add in the cocoa powder. Whisk until smooth.
Add in sour cream and vanilla extract. Continue to whisk until the sour cream is incorporated.
In a separate bowl, add in cake flour, sugars, baking soda, and baking powder. Whisk until combined.
Pour the cocoa/sour cream mixture in with the dry ingredients. Add in the lightly beaten eggs. Whisk until the batter is incorporated and smooth. I added in the eggs a little later to avoid cooking my eggs in the very hot liquid.
Add in the Irish whiskey and whisk until combined.
Pour the batter into the prepared bundt pan. Spread it out evenly and give it a few taps on the counter to remove any air bubbles.
Place into the oven and bake for 38 minutes or until a toothpick comes out moist crumbs or clean.
Remove from the oven and let cool for about 30 minutes.
Once the cake has cooled for 30 minutes, turn the bundt cake out onto a wire rack. Gently lift one side of the bundt pan to help loosen the edges of the cake. Then lift the opposite side to loosen that side. Repeat until cake comes out. Let cool completely on wire rack.
Place cooled bundt pan on a cake plate.
In a medium sized microwave-safe bowl, add in the milk chocolate chips and heavy cream.
Microwave for 30 seconds and stir. Repeat microwaving for only 30 seconds and stirring after each interval until the ganache is smooth. It normally takes 3 zaps in the microwave and stirring vigorously for it to come together.
After the ganache has come together, add 1 - 2 teaspoons of irish whiskey into the ganache. Stir until incorporated. This step is completely optional.
Let the ganache cool slightly. I would save about 30 minutes. You want the ganache to still have a nice drizzle consistency, but thicker than when it first came out of the mmicrowave.
Pour the ganache into a sandwich bag or disposable piping bag. Cut a small hole in the corner of the sandwich bag.