1-First step: prep your pan and oven
Start by preheating your oven to 350°F. Line a 12-cup muffin pan with paper liners so the cupcakes release easily after baking. This step sounds basic, but it sets you up for even baking and tidy cleanup. If you are baking for a crowd, you can line a second pan now so the batter does not sit too long while you wait.
Before you mix anything, make sure the eggs and buttermilk are at room temperature. Room-temperature ingredients blend more smoothly, which helps the batter bake evenly. If you forgot to take them out early, place the eggs in warm water for a few minutes and let the buttermilk sit on the counter while you gather the dry ingredients.

2-Second step: mix the dry ingredients
In a medium bowl, whisk together the flour, cocoa powder, espresso powder, baking powder, baking soda, and salt. Whisking helps break up cocoa lumps and spreads the leavening evenly through the mixture. That means every cupcake rises nicely instead of turning out lopsided or dense.
If your cocoa powder looks clumpy, sift it first. Natural cocoa tends to pack together, and a quick sift gives you a smoother batter. This is a small step, but it makes the final texture better.

3-Third step: blend the wet ingredients
In a large bowl, whisk the eggs, granulated sugar, and brown sugar until combined. Add the oil and vanilla, then whisk again until the mixture looks smooth and glossy. The oil gives these Chocolate Cupcakes their soft crumb, while brown sugar brings a little extra moisture and a deeper flavor.
Next, add the buttermilk and mix just until combined. Do not worry if the batter looks slightly loose at this stage. That is exactly what you want for tender cupcakes. If you are using melted coconut oil, let it cool a little first so it does not scramble the eggs.

4-Fourth step: bring the batter together
Add the dry ingredients to the wet ingredients and fold gently with a spatula or whisk. Stop mixing as soon as you no longer see streaks of flour. Overmixing can toughen the cupcakes, and nobody wants a dry cupcake after all this work.
The batter should look smooth and somewhat thin. That thin texture helps the cupcakes bake up light and moist. If you are baking for someone who wants a stronger chocolate hit, this is a great batter to pair with a dark chocolate frosting or a simple ganache.

5-Fifth step: fill the liners
Divide the batter evenly among the liners, filling each one about 2/3 full. This gives the cupcakes room to rise without spilling over. If you overfill the liners, the tops can dome too much and then sink in the middle as they cool.
A cookie scoop works well here because it keeps the portions even. Even baking means the cupcakes finish at the same time, which makes life easier when you are serving family, friends, or a classroom full of hungry kids.

6-Sixth step: bake with care
Bake for 18 to 22 minutes, or until the tops spring back lightly when touched and a toothpick inserted into the center comes out with a few moist crumbs. Keep an eye on them near the end of the baking time because ovens can run hot or cool. If you know your oven tends to bake unevenly, rotate the pan once during baking.
Do not open the oven door too early. A sudden drop in heat can cause the cupcakes to collapse. If you are baking at high altitude or in a very dry climate, check them a minute or two early since they may finish faster.

7-Seventh step: cool before decorating
Let the cupcakes cool in the pan for about 5 minutes, then move them to a wire rack. Cooling in the pan helps the structure set, while moving them to a rack keeps the bottoms from getting soggy. Once they are completely cool, add frosting and sprinkles for decorating.
If you frost too soon, the topping will slide right off, and that is never a fun kitchen moment. For a party look, add sprinkles just before serving so they stay bright and cheerful.