I use the Down-home Chocoalte Mayonnaise Cake recipe from The Cake Bible.
1/3 C unsweetened cocoa
1 C boiling water
1 tsp vanilla
3/4 C mayonnaise
2 C sifted cake flour
1 C sugar
2 tsp baking soda
1/2 tsp salt
Preheat oven to 400 degrees (the secret to domed cupcakes is to overheat the oven and turn down heat when you put the cupcakes into the oven).
In a medium bowl whisk together cocoa and boiling water until smooth and cool to room temp. Whisk in mayonnaise and vanilla.
In a large mixing bowl combine the remaining ingredients and mix on low speed for 30 seconds. Add chocolate mixture. Mix on low speed until dry ingredients are moistened. Increase to medium speed (high if using a hand mixer) and beat for 1 minute to aerate and develope cakes structure.
Using an ice cream scoop, scoop one level scoop into each cc liner. Place in oven and reduce tempurate to 350 degrees. Bake for 18-20 minutes or until cc's spring back when touched. Recipe should make 12 cupcakes.
I have successfully used this recipe on several occassions and I always dip them in ganache and they come out perfect every time. Here's the link to the pics.
Good luck and enjoy.