Chocolate Cupcakes

Preheat the oven to 350°F and set two oven racks in the centermost positions. Line two 12-cup muffin tins with paper liners.

In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, sugar, cocoa powder, salt, baking powder, and baking soda. Mix on low speed for 30 seconds to combine. Add the eggs, oil, sour cream, and vanilla and mix on low speed until combined.

Increase the speed to medium and beat for 2 minutes. Then, reduce the speed to low and gradually pour in the hot water (be careful to pour very slowly so it doesn’t splash). The batter will be soupy. Stop the mixer and scrape down the sides and bottom of the bowl; mix again until evenly combined.

Pour the batter evenly into the prepared muffin tins (they should be about halfway full). Bake for 18 to 20 minutes, or until the cupcakes are set and a toothpick inserted into the center of a cupcake comes out clean.

Cool the cupcakes in the pans for about 10 minutes, then transfer them to a wire rack to cool completely.

For the frosting, place the chocolate in a microwave-safe bowl and cook in the microwave in 20-second intervals, stirring in between, until about three-quarters of the way melted. Stir, allowing the residual heat in the bowl to melt the remaining chocolate completely. Set aside to cool.

In a food processor, process the butter, sugar, cocoa powder and salt until smooth, about 30 seconds, scraping down the sides of the bowl as needed. Add the corn syrup and vanilla and process until just combined, 5 to 10 seconds. Scrape down the sides of the bowl, then add the lukewarm chocolate and pulse until smooth and creamy, 10 to 15 seconds. Do not overmix. The frosting can be used immediately or held at room temperature for up to 3 hours.

When the cupcakes are completely cool, use a small offset spatula or butter knife to swirl the frosting lavishly over top.