Ingredients
Equipment
Method
Step 1: Prepare the Cake Pans
- I greased the pans with butter and lined the bottoms with parchment paper. That way, the cake came out clean every time.
Step 2: Mix the Dry Ingredients
- In a large bowl, I whisked together flour, cocoa powder, sugar, baking powder, baking soda, and salt.
Step 3: Add Wet Ingredients
- I added the eggs, buttermilk, oil, and vanilla into the dry mixture. I beat everything until smooth. Then I slowly poured in the hot coffee while mixing. The batter looked thin, but that’s what makes the cake so moist.
Step 4: Bake the Cake
- I poured the batter evenly into the pans and baked at 350°F (175°C) for 35 minutes. I tested the center with a toothpick—it came out clean. I let the cakes cool on a rack completely before frosting.
Step 5: Make the Mousse Filling
- In a small saucepan, I heated the cream until it started to bubble. I poured it over the chocolate chips in a bowl, waited a minute, then stirred until smooth. Once cool, I whipped it with powdered sugar until light and fluffy.
Step 6: Assemble the Cake
- I spread the mousse over one cake layer and topped it with the second layer. I chilled the cake while I made the ganache.
Step 7: Ganache Frosting
- I heated the cream until just simmering, poured it over the chopped chocolate, and added butter. After letting it sit, I stirred until glossy. Once slightly cooled, I poured it over the cake and spread it smoothly with a spatula.
Notes
If you want that true Costco-style experience, let the cake chill in the fridge for a few hours before serving—but bring it back to room temperature about 30 minutes before slicing.
That’s when the mousse softens, the ganache gets glossy, and the flavors fully bloom. I never skip this step—it makes all the difference.
Also, if you’re baking ahead for a party, this cake holds up beautifully in the fridge for up to 3 days. Just keep it covered to lock in the moisture.