01 - Preheat oven to 350°F. Grease and line a 9-inch round cake pan with parchment paper.
02 - In a large bowl, sift together all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt.
03 - In a separate bowl, whisk together granulated sugar, light brown sugar, vegetable oil, eggs, and vanilla extract until smooth. Blend in whole milk until fully incorporated.
04 - Gradually mix the dry ingredients into the wet mixture until just combined. Stir in hot coffee and mix until the batter is smooth.
05 - Pour batter into the prepared pan and bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean.
06 - Allow cake to cool in the pan for 10 minutes, then remove and place on a wire rack to cool completely.
07 - Heat heavy cream in a small saucepan until just simmering. Pour over chopped dark chocolate and let sit for 2 minutes. Add unsalted butter and stir until the ganache is smooth and glossy.
08 - Pour ganache over the cooled cake, letting it drip down the sides. Smooth the top and edges with a spatula.
09 - Place chopped white chocolate in a microwave-safe bowl and heat in 20-second intervals, stirring between each, until melted and smooth.
10 - Transfer melted white chocolate to a piping bag or a plastic bag with a small tip. Pipe concentric circles over the ganache, then drag a toothpick from the center outward to form a spiderweb pattern.
11 - Allow cake to set at room temperature or refrigerate briefly until the ganache is firm before serving.