Preheat your oven to 350°F (no fan). Grease and line three 8-inch cake pans with parchment paper and butter.

In a large bowl, whisk together flour, baking powder, baking soda, granulated sugar, light brown sugar, and salt. Set aside.

In a separate bowl, whisk together the eggs, vegetable oil, buttermilk, and sour cream until smooth.

Gradually add the dry ingredients into the wet ingredients in two additions. Mix gently until combined. Do not overmix.

In a small bowl, whisk together cocoa powder and instant coffee with boiling water until smooth. Add this to the batter and fold it in until combined.

Distribute the batter equally among the three prepared pans. Bake for 22-24 minutes, or until a toothpick inserted into the center comes out with moist crumbs. Let the cakes cool in the pans for 20 minutes, then transfer to a wire rack to cool completely.

In a saucepan, melt dark chocolate and corn syrup over low heat. Set aside. In a stand mixer, beat the cream cheese until smooth. Add cocoa powder, powdered sugar, and salt, and mix until creamy. Gradually add the melted chocolate and mix in the heavy cream until fluffy and smooth.

Trim the domes from the cooled cakes and layer them with chocolate fudge frosting. Apply a crumb coat and refrigerate for 20 minutes to set. Next, apply the remaining frosting over the cake.

Cut and serve the cake at room temperature to enjoy its full flavor and texture.