For the Chocolate Cake:

• 1 and 1/2 cups all-purpose flour
• 1 cup granulated sugar
• 1/2 cup unsweetened cocoa powder
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/2 teaspoon salt
• 2 large eggs
• 3/4 cup buttermilk
• 1/2 cup vegetable oil
• 2 teaspoons vanilla extract
• 3/4 cup hot water

For the Chocolate Mousse:

• 8 ounces semi-sweet chocolate, chopped
• 2 cups heavy cream
• 1/4 cup powdered sugar
• 1 teaspoon vanilla extract

For Decoration (Optional):

• Chocolate shavings
• Fresh berries
• Whipped cream

Instructions:

1. Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan, then line the bottom with parchment paper for easy removal.
2. In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until well combined.
3. Add the eggs, buttermilk, vegetable oil, and vanilla extract to the dry ingredients. Mix until smooth and well combined.
4. Gradually pour in the hot water while mixing on low speed until the batter is smooth. The batter will be thin, but that’s okay!
5. Pour the batter into the prepared cake pan and smooth the top with a spatula. Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
6. Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.
7. While the cake is cooling, prepare the chocolate mousse. Place the chopped semi-sweet chocolate in a heatproof bowl. In a small saucepan, heat 1/2 cup of heavy cream over medium heat until it just begins to simmer. Pour the hot cream over the chopped chocolate and let it sit for 1-2 minutes. Then, gently whisk until the chocolate is melted and the mixture is smooth. Allow it to cool to room temperature.
8. In a separate bowl, whip the remaining 1 and 1/2 cups of heavy cream with powdered sugar and vanilla extract until stiff peaks form.
9. Gradually fold the cooled chocolate mixture into the whipped cream until well combined and no streaks remain.
10. Once the cake has cooled completely, carefully slice it horizontally into two even layers using a serrated knife.
11. Place one layer of the cake on a serving plate or cake stand. Spread a generous layer of chocolate mousse over the top. Place the second layer of cake on top and cover the entire cake with the remaining chocolate mousse.
12. Refrigerate the cake for at least 4 hours, or overnight, to allow the mousse to set.
13. Before serving, decorate the cake with chocolate shavings, fresh berries, and whipped cream if desired.
14. Slice and serve this heavenly chocolate mousse cake to your guests, and watch as they indulge in every decadent bite! Enjoy the rich chocolate flavor and velvety texture of this exquisite dessert.