Prep your tools. Preheat the oven to 325F. Butter the bottoms and sides for two 8-inch round cake pans. Line the bottom of each pan with a round of parchment paper and grease the paper with PAM.

Make the chocolate mixture. Place the cocoa powder in a medium bowl. Add the hot water and whisk until smooth. Let cool to room temperature.

Combine dry ingredients. In a large mixer bowl, combine the brown sugar, flour, baking soda, and salt. With the mixer on low, blend to mix.

Beat. Add the butter and dissolved cocoa. Beat briefly to blend. Then raise the speed to medium and beat until light and fluffy, about 2 minutes.

Add liquid ingredients. In a medium bowl, whisk the eggs with the vanilla and cold water until blended. Add this liquid to the batter in 3 additions, scraping down the sides well and mixing only to incorporate between additions.

Bake. Divide the batter among the prepared cake pans. Bake for 40-45 minutes, or until a cake tester or wooden toothpick inserted into the center comes out almost clean, with just a few crumbs sticking to the pick.

Cool. Let cool in the pans for 15 minutes. Invert onto wire racks, carefully peel off the paper lines and let cool completely.

Make the fudge frosting. Place all the ingredients in a food processor and pulse to incorporate. Then process until the frosting is smooth. That’s it!

Assemble the cake. To assemble your cake, place one cake layer, flat side up, on a cake stand or a serving plate. Cover it with about 2/3 cup of frosting. Repeat with the next layer. Frost the top and sides of the cake, reserving some frosting to pipe swirls on top (if you want, you can also just use all the frosting at this stage). You can use the back of a palette knife or the back of a spoon to make swirls in the frosting too.

Make the ganache. In a small saucepan combine the chocolate and butter and melt over low heat. Let cool until just slightly warm but still pourable, then drizzle over the frosted cake as desired.

Add frosting swirls. If you want to add swirls of frosting on top of the ganache, add your reserved frosting to a piping bag with your desired tip. Pipe on top of the cooled ganache in your desired pattern.

Add chocolate shavings. Using a cheese grater with large holes, roughy grate your chocolate and sprinkle it on top of the cake. You can also use finely chopped chocolate, or chocolate sprinkles.