• Preheat the oven to 350 degrees Fahrenheit (177 degrees Celsius). Line one cupcake pan with cupcake liners, then set aside.
• In a medium-sized mixing bowl, whisk or sift together the flour, cocoa powder, sugar, baking soda, baking powder, and salt.
• In the bowl of a stand mixer, add the eggs, warm water with espresso powder, buttermilk, oil, and vanilla. Mix on medium speed until smooth. Turn the speed down to low and slowly add the dry ingredients to the wet mixture. Mix until smooth, making sure there are no pockets of dry flour or cocoa left, about 3 minutes.
• Divide the batter evenly among the cups, filling each about 2/3 full. Place in the oven and bake for 20–21 minutes, or until the tops spring back when touched and a cake tester or toohpick comes out clean. Be careful not to overbake!
• Remove from the oven, allow them to sit for 3–4 minutes in the pan, and then transfer to a wire rack to cool.

To Make the Cream Filling

• Whisk together the flour and milk in a small saucepan. Place over medium heat. Whisk continuously until it begins to thicken (watch it carefully, as it thickens quickly and can clump if left unattended). Let it cook for a couple of minutes, until the mixture has the consistency of pudding. Remove from the heat, whisk out all clumps, and place in the refrigerator to cool completely. The mixture must be chilled all the way through before adding it to the butter, or it will melt it.
• In the bowl of a stand mixer, beat the butter, sugar, vanilla, and salt for 2 minutes on medium-high speed using the whisk attachment. Add the flour and milk mixture. Beat on high for 6–8 minutes until the mixture is light and fluffy (it should resemble whipped cream in both texture and appearance). Chill in the refrigerator.
• When the cupcakes are completely cooled, remove a dime-sized section from the top, and using a sharp knife (cut out a neat circle, keeping the top part fully intact—you’ll need this piece later to seal the hole after filling), then make a hole for the filling (or use a cupcake corer if you have one, but be sure the cavity is wide and deep enough to hold a generous amount of filling—the more, the merrier). Pipe the filling into each hole and place the top back on, making sure it is flush with the rest of the cupcake.

To Make the Ganache

• Heat the cream in a small saucepan over medium heat. In a separate bowl, combine the chocolate, corn syrup, and vanilla. Once the cream is heated through, pour it over the chocolate and whisk until smooth. Let cool for 10 minutes or so before using it.
• Once the ganache is cooled, turn the cupcakes over and dip, making sure to cover the top completely and remove the excess by swirling in circles and allowing it to drip. Continue the process with each cupcake, then go back and re-dip each cupcake two more times (this helps build a thick, even coating that also conceals the filled center).
• Place the cupcakes in the refrigerator for 10 minutes so the ganache can solidify. Meanwhile, to make the icing, in the bowl of a stand mixer, beat the butter until creamy. Add the salt and vanilla. Combine. With the speed on low, slowly add the powdered sugar, then the milk. Beat until smooth and fluffy. Pipe the icing onto each cupcake as desired.