01 -
Adjust oven rack to the 2nd level position (just above center) and preheat to 350ºF. Generously spray a 6-inch cake pan with flour-based baking spray or grease and flour. Optionally, add a 6-inch parchment paper circle to the bottom of the pan.
02 -
In a microwaveable bowl, melt the dark chocolate in 30-45 second increments until smooth and creamy. Set aside to cool slightly.
03 -
In a small mixing bowl, whisk together the flour, granulated sugar, light brown sugar, cocoa powder, baking powder, baking soda, and salt. Set aside.
04 -
In a separate medium-size mixing bowl, whisk together the egg, milk, vegetable oil, vanilla extract, and hot water with dissolved espresso powder (if using).
05 -
Incorporate the melted chocolate into the wet ingredients mixture.
06 -
Add the dry ingredients to the wet ingredients and whisk until just combined. Be careful not to over mix the batter.
07 -
Pour the batter into the prepared cake pan and bake for 25-28 minutes at 350ºF or until an inserted toothpick comes out clean.
08 -
Allow cake to cool in the pan for 10 minutes before inverting onto a wire cooling rack to cool completely.
09 -
In a microwaveable bowl, melt the milk chocolate chips in 30-45 second increments until smooth and creamy. Set aside to cool slightly.
10 -
Using a hand mixer or stand mixer fitted with a paddle attachment, mix the butter, sifted powdered sugar, cocoa powder, and salt on medium speed until well blended. Scrape down the sides of the bowl as needed.
11 -
Add the corn syrup, vanilla extract, and melted chocolate to the mixture, and mix until the frosting is well blended and smooth in texture.
12 -
Once the cake is completely cooled, frost it with the milk chocolate frosting and top with rainbow jimmies if desired.