Prep the pans. Heat your oven to 350°F (175°C). Grease and line two 8-inch round cake pans with parchment. Lightly flour the sides to prevent sticking.

Mix the dry ingredients. In a large bowl, whisk flour, cocoa, granulated sugar, brown sugar, baking powder, baking soda, and salt until evenly combined.

Whisk the wet ingredients. In a separate bowl or large measuring cup, beat eggs, milk, oil, and vanilla until smooth.

Combine wet and dry. Pour the wet mixture into the dry ingredients. Stir with a whisk or spatula until just blended. The batter will be thick at this point.

Add the hot liquid. Pour in the hot coffee (or hot water) and whisk gently until the batter is smooth and glossy. It will be thin—this is normal and makes a moist cake.

Bake. Divide the batter between the pans. Bake for 28–32 minutes, or until a toothpick comes out with a few moist crumbs. Do not overbake.

Cool completely. Let the cakes rest in the pans for 10 minutes, then turn out onto a wire rack and cool completely before frosting.

Make the fudge frosting. In a saucepan over medium heat, melt the butter. Whisk in the cream and cocoa powder until smooth and just starting to steam. Remove from heat.

Finish the frosting. Gradually whisk in the powdered sugar, vanilla, and salt until thick, glossy, and spreadable. If it’s too thick, add a splash of cream. If too thin, whisk in a bit more powdered sugar. Let it cool for 5–10 minutes to thicken slightly.

Assemble the cake. Place one cooled layer on a plate. Spread a generous layer of frosting over the top. Set the second layer on and frost the top and sides. Work fairly quickly; this frosting sets as it cools.

Let it set. Allow the frosted cake to rest for 20–30 minutes so the frosting firms up. Slice and serve.