• Preheat oven to 325 degrees F. Grease 2 9-inch cake pans with butter, then coat with flour. Then trace the bottom of the cake pans onto parchment paper, cut out the circles, and put them in the bottom of the pan.*
• In a medium saucepan, melt 1 cup butter over medium heat. Stir in the water and cocoa and whisk until combined. Bring to a boil over medium heat and boil for about 30 seconds. Remove pot from heat and let sit aside to cool.
• Meanwhile, in a large bowl, whisk together the white sugar, flour, and 3/4 teaspoon salt.
• In another medium bowl, whisk together 2 eggs. Slowly sprinkle baking soda and baking powder over the top while you whisk. Beat until there are no lumps. The mixture may foam, and that's ok!
• Stir in the vanilla and 1 cup brown sugar.
• When the chocolate mixture in the pot has cooled enough to handle, stir it into the flour mixture. Then add the egg mixture. Each time mix only until combined.
• Lastly, fold in the sour cream. DON'T over mix!!
• Divide the batter evenly between the 2 pans (I use a scale). Drop the cakes on the counter from a few inches above to get out some of the air bubbles.
• Bake for about 34-40 minutes, rotating the pans halfway through. Remove from the oven when a toothpick comes out of the center clean.
• Let cakes cool in the pans for 10 minutes, then carefully loosen edges with a knife and invert onto a cooling wrack. Let cakes cool completely.
• Wrap the cakes securely in plastic wrap and freeze for about an hour or 2. (This is only so that it's easy to frost the cake. If you are in a hurry and presentation isn't an issue, frost as soon as they are cool!)

Make the frosting:

• UPDATE: It's 2025 and I have a new favorite Chocolate Buttercream Frosting recipe! Tap to view. Either recipe is super amazing! But I love the new one slightly more.
• Cream the butter well. Add the cocoa and powdered sugar in increments, adding the cream in between. Beat well after each addition. Add the salt and vanilla.
• Smear a bit of frosting on the bottom of a cake plate. Place 1 frozen cake on top, then cover the top with about 1 cup of frosting (I like to use an offset spatula).
• Place the other cake on top, then frost the outside and edges. If you don't want your cake plate to get frosting all over it, line it with strips of parchment paper that you can pull out when the cake is completely frosted.
• Serve with lots of milk!