Ingredients

• 2 cups all-purpose flour
• 1 1/2 teaspoons baking soda
• 1/2 teaspoon salt
• 1 cup unsweetened cocoa powder
• 1 2/3 cups boiling water
• 1 cup unsalted butter, room temperature
• 2 cups sugar
• 1 1/2 teaspoons vanilla extract
• 3 large eggs
• 10 ounces good-quality white chocolate, chopped
• 1 3/4 cups chilled whipping cream
• 1/4 cup sour cream
• 24 red-and-white-striped hard peppermint candies (about 2/3 cup) or 12 candy canes, crushed (about 2/3 cup)
• 2 cups whipping cream
• 16 ounces semisweet chocolate, chopped

Instructions

1. Make cake:

2. 1- Preheat oven to 325 °F.

3. 2- Butter and flour three 9-inch-diameter cake pans with 1 ½-inch-high sides.

4. 3- Whisk flour, baking soda, and salt in small bowl to blend.

5. 4- Place cocoa in medium bowl; whisk in 1 2/3 cups boiling water. Cool cocoa mixture to room temperature, whisking occasionally.

6. 5- Using electric mixer, beat butter in large bowl until fluffy. Gradually beat in sugar, then vanilla. Beat in eggs 1 at a time.

7. 6- At low speed, beat in flour mixture in 3 additions alternately with cocoa mixture in 2 additions.

8. 7- Divide batter equally among prepared pans. Bake cakes until tester inserted into center comes out clean, about 30 minutes. Cool cakes in pans 10 minutes. Cut around cakes to loosen. Turn out onto racks/plates lined w/ wax paper so they don’t stick. Cool completely.

9. Make peppermint mousse:

10. 1- Combine white chocolate, ¾ cup whipping cream, and sour cream in heavy medium saucepan. Stir over low heat just until chocolate is melted and smooth.

11. 2- Transfer white chocolate mixture to large bowl; cool to barely lukewarm, whisking occasionally, about 20 minutes.

12. 3- Mix in candies.

13. 4- Beat remaining 1 cup cream in medium bowl to soft peaks. Fold cream into barely lukewarm white chocolate mixture in 4 additions.

14. 5- Chill mousse until beginning to set, about 2 hours.

15. 6- Place 1 cake layer on cardboard round or cake tray. Spread half of mousse over top of cake. Top with second cake layer, remaining mousse, and third cake layer. Chill assembled cake until mousse is cold & set, about 3 hours (can be made a day ahead).

16. Make ganache:

17. 1- Bring cream to simmer in heavy large saucepan.

18. 2- Remove from heat. Add semisweet chocolate; whisk until melted & smooth.

19. 3- Cool ganache until thick but still pourable, about 45 minutes.

20. 4- Place cake on rack or baking sheet. Pour ganache over cake, spreading with metal spatula to cover sides evenly.

21. 5- Chill cake till ganache sets, at least 30 minutes & up to 1 day.