In a small bowl, combine the marshmallow fluff, cornstarch, and ¼ cup of water. Whisk the ingredients together until the mixture is smooth and free of lumps. This will form the creamy marshmallow filling.
Step 3: Make the Whipped Cream
In a separate bowl, whip the heavy cream, powdered sugar, and vanilla extract together until stiff peaks form. This will create a fluffy, sweet whipped cream layer for the cake.
Step 4: Assemble the Cake
Once the cake has completely cooled, use a serrated knife to cut the cake in half horizontally to create two layers. This will give you the perfect layers for filling and stacking.
Spread the marshmallow fluff mixture evenly over the bottom layer of the cake, ensuring it’s smooth and fully covered.
Top the marshmallow layer with the whipped cream mixture, spreading it evenly to create a fluffy, creamy layer.
Place the top layer of the cake over the whipped cream layer, gently pressing down to secure it.
Step 5: Make the Chocolate Ganache Topping
In a microwave-safe bowl, combine the semi-sweet chocolate chips and butter. Microwave in 20-second intervals, stirring in between each, until the mixture is smooth and fully melted.
Pour the chocolate ganache over the top of the cake, spreading it evenly with a spatula so it covers the entire surface.
Step 6: Let the Cake Set
Allow the chocolate ganache to set before slicing and serving. You can place the cake in the refrigerator for about 30 minutes to help the ganache firm up more quickly.
Step 7: Serve and Enjoy
Once the ganache has set, slice the cake and serve. This cake is rich, creamy, and perfect for any occasion—whether it’s a celebration or just a special treat for yourself!
