1. Preheat and Prepare Pans

• Preheat oven to 350°F (175°C).
• Grease and line two 8-inch round cake pans or one 9×13-inch pan with parchment paper.
• Lightly dust pans with cocoa powder instead of flour for a cleaner finish.

2. Mix Dry Ingredients

• In a large mixing bowl, sift together flour, cocoa powder, baking powder, baking soda, and salt.
• Whisk to combine evenly and remove lumps.

3. Mix Wet Ingredients

• In a separate bowl, whisk together eggs, sugar, brown sugar, oil, buttermilk, and vanilla extract until smooth and creamy.
• Stir in hot water or coffee slowly—this enhances the chocolate flavor and loosens the batter.

4. Combine Wet and Dry

• Pour the wet ingredients into the dry mixture and whisk until just combined—avoid overmixing.
• Fold in chopped chocolate or chocolate chips if using for extra fudgy texture.

5. Bake the Cake

• Divide batter evenly between prepared pans.
• Bake for 30–35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
• Let cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

6. Prepare the Frosting

For Ganache:

• Heat cream until just simmering and pour over chopped chocolate. Let sit for 2 minutes, then stir until smooth.
• Add butter for extra shine and richness if desired. Let ganache cool slightly to thicken before spreading or pouring over cake.

For Buttercream:

• Beat softened butter until light and fluffy.
• Add cocoa powder and powdered sugar gradually, mixing well between additions.
• Add vanilla and enough milk or cream to reach spreadable consistency.

7. Frost the Cake

• Once cakes are completely cool, spread ganache or buttercream over one layer.
• Add the second cake layer and cover top and sides with frosting.
• Use a spatula to smooth or create swirls. Decorate as desired.

8. Chill and Serve

• Let cake set for 20–30 minutes before slicing.
• Store covered at room temperature for 2 days or in the fridge for up to 5 days.