Instructions

For the chocolate cake layer

1. Preheat oven to 350 F. Grease and flour or use cooking spray on a 9" round baking pan.
2. In the bowl of your stand mixer, combine the sugar, flour, cocoa powder, baking powder, baking soda and salt. 
3. Make a well in the middle of the dry ingredient mixture and add in the egg, milk, vegetable oil and vanilla extract. Beat for 2 minutes on medium speed, then stir in the boiling water.
4. Pour the mixture into the baking pan. Bake for 10-15 minutes or until a toothpick comes out clean. Let the cake cool in the pan for 10 minutes, then flip it out onto a wire rack to cool completely before moving on to the next layer. 

For the raspberry mousse layer

1. Prepare your pan before beginning this layer. You will need a 9 or 9 1/2 inch round pan with sides at least 2 1/2 inches tall and the ability to remove the bottom. Either a springform pan or cake pan with removable bottom will work. Line the inner wall of the pan with a 4-inch high strip of wax paper or foil or acetate cake collar. Make sure the strip overlaps.
2. Place a cake cardboard in the bottom of the pan. Place the chocolate cake layer on top of the cardboard. 
3. Blend the raspberries in your blender to create a puree. Pour them through a fine mesh strainer to remove the seeds.
4. In a double boiler combine the raspberry puree, white chocolate chips and 1/2 cup of the heavy cream. Stir over medium heat until the chocolate is melted. Pour into a large bowl and let cool to room temperature, stirring occasionally. 
5. While you wait for the raspberry chocolate mixture to cool, whisk together the powdered gelatin and cold water in a small bowl. Let sit until the raspberry chocolate mixture is at room temperature, then microwave the bowl of gelatin for 15 seconds, until melted. Whisk the gelatin and chocolate together. 
6. Place the remaining 1 cup heavy cream in the bowl of your stand mixer and whip until firm peaks form. Fold half of the whipped cream into the raspberry chocolate mixture until combined. Then fold in the remaining whipped cream. 
7. Spread the raspberry mousse over the cake layer. Refrigerate for 25 minutes or until the mousse layer is set enough to add another layer.

For the chocolate mousse layer

1. In a double boiler combine the dark chocolate chips and 1/2 cup of the heavy cream. Stir over medium heat until the chocolate is melted. Pour into a large bowl and let cool to room temperature, stirring occasionally. 
2. While you wait for the chocolate mixture to cool, whisk together the powdered gelatin and cold water in a small bowl. Let sit until the chocolate mixture is at room temperature, then microwave the bowl of gelatin for 15 seconds, until melted. Whisk the gelatin and chocolate together. 
3. Place the remaining 1 cup heavy cream in the bowl of your stand mixer and whip until firm peaks form. Fold half of the whipped cream into the chocolate mixture until combined. Then fold in the remaining whipped cream. 
4. Take the cake pan with the raspberry mousse layer out of the refrigerator and spread the chocolate mousse layer on. Try to get the top as smooth as possible. Refrigerate for at least 4 hours or overnight so that the mousse is well set. 

For the mirror glaze

1. Before you start working on your mirror glaze, move your cake to the freezer to be sure it is really cold when you put on the glaze. 
2. Whisk together the cold water and powdered gelatin in a small bowl, set aside. Place the dark chocolate chips in a medium sized glass or metal bowl and set aside.
3. Place sweetened condensed milk, water, sugar and cocoa powder in a saucepan. Bring to a boil and remove from the heat. Stir in the gelatin mixture until it is dissolved. 
4. Pour the hot cocoa and gelatin mixture over the dark chocolate chips. Let sit, stirring occasionally until the chocolate is melted or about 5 minutes. Use an immersion blender to blend until smooth. Pour the glaze through a sieve to remove any lumps. Let cool for a few minutes until just above room temperature. 

Assembling the cake

1. While you wait for the glaze to cool, line a baking sheet with parchment paper and place a bowl that is smaller than your cake pan on it. Take the cake out of the freezer and place it on the bowl. Use a hair dryer to slightly defrost the sides so that you can remove sides of the pan. Remove the bottom of the pan (leaving the cake cardboard under the cake) and then place the cake back on the bowl. Remove the strip from around the cake.
2. Pour the glaze over the cake. Use a spatula to remove the drips around the bottom. Transfer the cake to a cake stand and put in the refrigerator for at least 30 minutes to set the glaze. 
3. Before serving, decorate with fresh raspberries and chocolate shavings if desired.