Preheat oven to 350°F (175°C)
Grease a bundt pan with cooking spray OR shortening, then add a pinch of cocoa powder and shake it around, regrease any missed spots and set aside
Sift together flour, cocoa powder, baking soda, and salt in a bowl
Combine the vanilla extract with 1 cup milk
In a large bowl, beat butter and sugar with a mixer until fluffy, about 1–2 minutes
Mix in the eggs one at a time, beating well after each addition
Gradually add the flour mixture and milk mixture to the butter mixture, mixing until just combined
Once the cake batter is mixed stir in the boiling water
Pour the batter into the prepared bundt pan
Bake for 1 hour 15 minutes, or until a toothpick inserted into the center comes out clean
Cool the cake in the pan for 10 minutes, then invert onto a plate to continue cooling for 1 hour