- Set the oven temperature to 350°F (175°C). Prepare cupcake liners for a 12-cup muffin tray. 
- Mix the dry ingredients: Combine the flour, sugar, baking soda, cocoa powder, baking powder, and salt in a big basin. 
- Combine wet ingredients: In a separate dish, thoroughly mix together eggs, buttermilk, oil, and vanilla extract. 
- Mix wet and dry ingredients together: Stir just until mixed after gradually adding the wet ingredients to the dry ingredients. Avoid over-mixing. 
- Add hot water: Until the batter is smooth, carefully stir in the hot water or coffee. It's okay if the batter is thin. 
- Pour the batter into each cupcake liner, filling it to about two thirds of the way. 
- Bake: Bake the muffin tin for 18 to 20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean. Preheat the oven. 
- Cool: After letting the cupcakes cool in the pan for roughly ten minutes, move them to a cooling rack to finish cooling. 
- While the cupcakes are cooling, get the frosting ready. Beat until creamy with the softened butter. Add the cocoa powder and powdered sugar gradually, beating on low speed until thoroughly blended.  
- Beat the frosting on high speed until it becomes light and fluffy after adding the milk and vanilla extract. 
- Once the cupcakes are completely cold, frost them.