Generously grease the bundt cake pan with cold butter. It will warm up as you move it around the pan with your fingers or brush. Be sure to get the butter into every corner of the pan. Put the buttered pan in the refrigerator while you make the batter. (Refrigerating the buttered pan will ensure that the butter coating doesn't move when the batter is poured into the pan).

Preheat the oven to 325 degrees.

In a stand mixer fitted with the paddle attachment, or in a bowl, beat the butter and sugar until light and fluffy, around 3-4 minutes. 

Add the eggs one at a time. Blend until incorporated. The batter may look  a little curdled. This is normal.

Use a spatula to scrape the bottom of the bowl to ensure that nothing is stuck to the bottom of the bowl.

Add the vanilla, coffee and half of the buttermilk. Blend until incorporated.

Mix all of the dry ingredients together with a whisk (flour, cocoa powder, baking powder, baking soda and salt). Add half of the dry ingredients to the batter. Blend on low speed until mostly incorporated. 

Add the other half of the buttermilk. Blend until incorporated.

Add the remainder of the dry ingredients and blend until mostly incorporated. Remove the bowl from the stand mixer. Finish mixing the batter by hand with a spatula.

Remove the cake pan from the refrigerator. If you're using an intricate cake pan, you may want to flour the pan for extra insurance. Pour the batter into the pan. 

Bake the cake at 325 degrees for 60 minutes, or until a toothpick comes out clean.

Allow the cake to cool for 15 minutes before flipping the cake onto a serving plate. Shake the pan from side to side to determine if it has released from the sides of the pan. If not, check again in five minutes. 

Place the chocolate chips in a microwave safe bowl. Place the chocolate in the microwave for 30 seconds, twice. Remove and stir the chocolate.

Add the whipping cream to the chocolate. Place in the microwave for 30 seconds. Remove and stir. Repeat until combined and smooth.