Preheat oven to 350°F (175°C). Grease and flour two 8-inch cake pans or line with parchment paper.,In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.,In another bowl, whisk eggs, granulated sugar, brown sugar, oil, milk, and vanilla extract until smooth.,Add wet ingredients to dry ingredients and mix until just combined.,Pour in hot water or coffee and stir until batter is smooth. It will be thin.,Divide batter between pans and bake for 30–35 minutes, or until a toothpick comes out clean.,Cool in pans for 10 minutes, then transfer to wire racks to cool completely.,In a chilled bowl, whip heavy cream until soft peaks form. Add powdered sugar and vanilla. Continue beating until stiff peaks form.,If using, fold in softened cream cheese for added structure and tang.,Place one cake layer on a serving plate. Spread cream filling evenly on top.,Add second cake layer. Optionally top with ganache, berries, or a dusting of cocoa powder.,Chill assembled cake for at least 1 hour before slicing. Serve cold or let sit for 15 minutes at room temp before serving.