Preheat the oven to 350°F (177°C) and grease and line three 6-inch (15.24 cm) cake pans.

In a medium bowl, whisk together the 2 ¼ cup flour, baking powder and salt. Set the dry ingredients aside.

In an electric mixer fitted with the whisk attachment, beat the butter, oil, C&H^® Granulated Sugar and C&H^® Light Brown Sugar together, on medium speed, until they’re light and fluffy. This should take 2 to 3 minutes. 

Add in the eggs, one at time, beating well after each addition for about 30 seconds. Make sure to scrape the bottom of the bowl as needed. Add in the sour cream and vanilla and mix just until they’re combined.

In five increments, alternate adding the dry ingredients and the milk into the batter, beginning and ending with the dry ingredients. Beat the mixture on medium speed, just until the flour is fully incorporated, making sure to scrape all the flour off the edge of the bowl.

Separate the batter in half, there should be about 5 ½ cups (45 oz) total. Add the reserved flour to one half and cocoa powder to the other half and mix just until combined. Place globs of both batters into the cake pans, distributing the batter evenly among all three. To create the marble effect, use a toothpick to swirl the batter back and forth a few times. 

Bake for about 35 minutes, until the cake springs back when it’s poked. Remove the cakes from the pans and allow them to cool completely before frosting.

Place the room temperature butter in the bowl of an electric mixer. Using a whisk attachment, beat the butter on medium-high speed for 1-2 minutes, until the color turns to a pale yellow.

Add the salt and the C&H^® Powdered Sugar to the butter and mix on low speed, just until combined. Turn the mixer to medium-high speed and beat the buttercream for at least five minutes, until all of the C&H^® Powdered Sugar is fully dissolved and the buttercream no longer feels gritty. Remember to scrape the bottom and edges of the bowl.

Pour in the heavy whipping cream and vanilla bean paste and beat for another 2 minutes on medium-high speed. If the buttercream is too soft to frost, refrigerate it while you make the chocolate ganache.

In a glass bowl, combine the dark chocolate with the heavy whipping cream. Microwave for 30 seconds, remove and mix. Microwave for 20 seconds, remove and mix. If there are still some tiny chocolate pieces that haven't melted, microwave for another 10 seconds. Mix until it's smooth and allow it to cool to room temperature.

If the cakes are domed, trim the tops off to make them flat. Use 1/4 of the buttercream to frost the first layer and then use 1/4 of the chocolate ganache on top of the frosting. Repeat for the second layer. Place the third layer on top, smooth out any buttercream that squeezes out between the layers and refrigerate the cake until it's firm. 

Remove the cake from the fridge. Place the rest of the buttercream on top of the cake and use an offset spatula to work its way down the sides. Use a cake scraper to smooth out the side and leave the rugged edge at the top of the cake as a border. Reheat the chocolate ganache for 10 seconds, mix it until it's smooth and pour on top of the cake, filling it to the frosting border. Top with chocolate shavings, coconut flakes, gold foil, blackberries and a dusting of powdered sugar (or whatever else you want).