Prepare the Pumpkin Cake:

• Preheat your oven to 350°F (175°C). Grease and line two 9-inch round cake pans.
• In a large bowl, whisk together flour, granulated sugar, brown sugar, baking powder, baking soda, cinnamon, nutmeg, and salt.
• In another bowl, mix eggs, pumpkin puree, vegetable oil, and vanilla extract until smooth. Combine with dry ingredients, mixing until just combined.
• Pour the batter into prepared pans and bake for 25-30 minutes, or until a toothpick comes out clean. Cool completely.

2. Make the Chocolate Mousse:

• Melt chocolate in a double boiler or microwave. Let cool slightly.
• Whip 1 cup of heavy cream until soft peaks form. Gradually add powdered sugar, whipping until stiff peaks form. Reserve ½ cup for topping.
• Mix egg yolks into the melted chocolate. Fold in the whipped cream, then gently fold in whipped egg whites until combined.

3. Assemble the Cake:

• Place one cake layer on a serving plate. Spread half of the mousse on top, then add the second layer and the remaining mousse.
• Refrigerate for at least 2 hours to set.

4. Prepare the Ganache:

• Heat cream until simmering, then pour over chocolate. Let sit for 5 minutes, then stir until smooth.
• Pour ganache over the cake. Garnish with reserved whipped cream and optional toppings.