Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans.
Mix Dry Ingredients:
In a large bowl, whisk together flour, sugar, cocoa, baking powder, baking soda, and salt.
Combine Wet Ingredients:
In another bowl, mix buttermilk, oil, eggs, and vanilla. Gradually stir into dry ingredients until combined.
Add Hot Water:
Slowly mix in hot water to create a smooth, thin batter.
Bake:
Divide batter evenly between pans and bake for 30–35 minutes, or until a toothpick comes out clean. Cool completely.
Prepare Galaxy Frosting:
Beat butter until fluffy. Gradually add powdered sugar and cocoa. Mix in milk and vanilla.
Divide frosting into separate bowls and tint each with your desired galaxy colors. Swirl together slightly for a marbled effect.
Assemble Cake:
Spread a layer of frosting on the first cake layer. Place the second layer on top and cover the entire cake with the swirled galaxy frosting.
Decorate:
Sprinkle candy pieces, edible glitter, or chocolate shavings to enhance the galaxy effect.
Serving and Storage Tips
