Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing them with butter and dusting with flour.

In a large mixing bowl, whisk together 2 cups all-purpose flour, 2 cups granulated sugar, ¾ cup unsweetened cocoa powder, 1½ teaspoons baking powder, 1½ teaspoons baking soda, and 1 teaspoon salt.

In a separate bowl, mix 1 cup buttermilk, ½ cup vegetable oil, 2 large eggs, and 2 teaspoons vanilla extract. Use a whisk to blend them well until smooth.

Stir the wet and dry ingredients together until just combined, gradually adding 1 cup of boiling water to the batter, stirring continuously until smooth.

Divide the batter evenly between the prepared cake pans and bake for 30 to 35 minutes, or until a toothpick comes out clean.

Carefully remove the cakes from their pans and place them on a wire rack to cool completely.

In a small pot, combine 2 cups fresh raspberries, ¼ cup granulated sugar, and 1 tablespoon lemon juice, cooking over medium heat until thickened.

Once thickened, strain the mixture through a fine-mesh sieve to remove seeds, yielding about ¾ cup of raspberry puree.

In a small bowl, combine 1 tablespoon unflavored gelatin powder with 3 tablespoons cold water. Let it sit for about 5 minutes to bloom.

In a chilled mixing bowl, whip 1 cup of cold heavy cream to stiff peaks, then gently fold in the warm raspberry mixture.

Heat 1 cup heavy cream until simmering, pour it over 8 ounces of finely chopped dark chocolate in a bowl, and stir until smooth.

Once the cakes have cooled, place one layer on a cake stand, spread half of the raspberry mousse on top, then add the second cake layer.

Refrigerate the assembled cake for at least 2 hours to allow the mousse to firm up.

After chilling, pour the cooled ganache over the cake and smooth the top using a spatula.

Garnish your cake with fresh raspberries and optional chocolate shavings or powdered sugar.