Combine butter and cocoa powder in a large heavy saucepan over medium-low heat, whisking, until butter is melted. Add milk and sugar, whisking until sugar dissolves, about 1 minute. Remove pan from heat and stir in whiskey and vanilla extract. Set aside to cool slightly.
While chocolate mixture cools, generously grease a 12-cup bundt pan, then dust with cocoa powder, knocking out excess. Place the pan in the refrigerator to chill while preparing the batter.
Whisk together flour, baking soda, and salt in a bowl and set aside. Whisk eggs into the cooled chocolate mixture until combined well. Add flour mixture and whisk until flour is incorporated and no lumps remain (batter will be thin and bubbly). Pour batter into chilled bundt pan and then sprinkle the chocolate chips evenly over the surface of the batter. Bake in an oven preheated to 325°F until a wooden pick or skewer inserted in center comes out clean, about 50 to 60 minutes.
Cool cake completely in pan on a rack, about 2 hours. Invert rack over pan and turn cake out onto rack.
For the glaze, place dark chocolate in a 2-cup measuring glass with a pour spout. Bring cream to a boil in a small saucepan over medium heat. Pour cream over the chocolate and let it sit without stirring for two minutes before mixing vigorously with a small spatula. Once the chocolate becomes smooth and glossy, add 1 tablespoon whiskey and mix until smooth.
Set the rack holding the cooled cake atop a baking sheet. Stir the ganache well before slowly drizzling the glaze over the cake. Allow the glaze to set for about 10 minutes before slicing.