Berry Chantilly Cake

For the cake layers

1. Preheat the oven to 325º F. Coat two 9-inch cake pans with cooking spray and line the bottom of the pans with parchment paper cut into rounds and line the sides with parchment paper cut into strips.
2. Soak two cake baking strips in water.
3. Place the butter and granulated sugar in the bowl of a mixer fitted with a paddle attachment and beat for about 2-3 minutes until combined.
4. Add the eggs, one at a time, scraping down the sides and beating after each addition.
5. Add the egg yolks, one at a time. Stir in the vanilla.
6. Stir together the salt, baking powder, and flour in a large bowl. Pour half of the flour mixture into the butter mixture and mix until just combined. Add half of buttermilk, then add the remainder of the flour mixture followed by the remainder of the buttermilk. Do not over mix.
7. Divide the cake batter evenly between the pans.
8. Squeeze out the excess water from the baking strips and secure around the pans. Bake for 55-60 minutes or until a toothpick inserted into the center comes out clean.
9. Remove from the oven and place the pans on a wire rack. Remove the baking strips and allow the cakes to cool for 10 minutes. Then, turn the cakes out on the cooling rack to cool completely.
10. Once cooled, wrap the cakes and store at room temperature if assembling the following day. If you are assembling the cake on the same day, freeze them for 30 minutes.

For the berry syrup

1. Combine the raspberry jam and water; heat in the microwave for 20 second increments or until melted.
2. Press through a sieve to remove seeds.

For the frosting

1. With a mixer fitted with the whisk attachment, beat the heavy cream and vanilla extract until stiff peaks just start to form. Transfer the whipped cream to a bowl. Keep a close eye on the cream once it starts to thicken to prevent over whipping it. If the cream is over whipped it will become grainy. If this happens, stir in some unwhipped cream until smooth.
2. Put the butter into the mixing bowl and beat until smooth. Add the mascarpone cheese, cream cheese, and powdered sugar and beat until very smooth.
3. Gently fold the whipped cream into the mascarpone mixture until completely incorporated. Use immediately or chill until you are ready to use it.

For the filling, decoration and assembly

1. Set aside a few strawberries for decoration. Hull the remainder and cut them in half or into quarters if they are quite large.
2. To create four even cake layers, first trim the tops off the cakes with a cake leveler or large serrated knife so that they are 1½ inch thick. Next, cut each cake in half so that you have four ¾ inch layers.
3. Spread a little frosting onto your serving plate or cake stand and attach the first cake layer onto it.
4. Brush the berry syrup over the cake layer.
5. Fit a piping bag with a large round tip, and half fill with frosting. Pipe a layer of frosting onto the cake (approximately 1 1/3 cups). If you don’t have a piping bag, spread a ¼ inch layer of frosting onto the layer with an offset spatula.
6. Arrange a mixture of the berries (approximately 2/3 cup) over the frosting layer.
7. Place the second cake layer on top. Brush the second layer with syrup and repeat the process from the first layer of adding the frosting and berries.
8. Add the third layer of cake, brush with syrup, spread with frosting and arrange more berries on top.
9. Place the final layer on top and crumb coat the whole cake by covering it in a very thin layer of frosting. Chill for 15 minutes.
10. Spread the remaining frosting over the cake with an offset spatula. To create a swirl finish, place the cake on a turntable and hold the offset spatula against the side of the cake. Turn the cake continuously as you slowly run the knife up the side of the cake. Repeat on the top starting in the middle and work out towards the edges.
11. Arrange the remaining berries and mint sprigs on top of the cake. The cake can be refrigerated for one day. Bring to room temperature before serving.