Preheat your oven to 350°F (175°C). Grease and flour an 8-inch round cake pan.

In a medium bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.

In another bowl, combine vegetable oil, eggs, buttermilk, and vanilla extract. Mix until smooth.

Gradually add the wet ingredients to the dry ingredients, stirring gently until just combined.

Pour the batter into the prepared pan and bake for 25-30 minutes. Cool completely.

In a saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat until thickened. Strain and cool.

Sprinkle gelatin over water in a small bowl and let sit for 5 minutes. Microwave until dissolved and stir into the cooled raspberry puree.

In a large bowl, whip heavy cream and powdered sugar until stiff peaks form. Fold in the raspberry mixture.

Heat heavy cream until just simmering. Remove from heat and stir in the chopped chocolate until smooth. Add vanilla extract.

Place the cooled chocolate cake on a serving plate. Spread raspberry mousse evenly over the cake.

Refrigerate for at least 2 hours to set. Pour chocolate ganache over the mousse and spread evenly.

Refrigerate for another hour before serving.