Line two 6" round cake pans with parchment paper. Set aside.

Separate egg whites from egg yolks while cold from the fridge.

Sift cake flour and baking powder into the egg yolk mixture and mix until just incorporated. Set aside.

Add in cream of tartar and continue whipping until foamy.

Transfer about ⅓rd of the egg white mixture into the egg yolk mixture and fold it in with a spatula.

Continue to fold in the egg white meringue mixture into the egg yolk mixture until all of it is incorporated, with no trace of white streaks.

Use a kitchen scale to divide the cake batter evenly between the two prepared cake pans.

Give the pans a few taps to release any trapped air bubbles.

Remove the cakes from the oven and immediately drop them onto the counter from a height of about 1' to prevent the cake from shrinkage.

Invert the cakes to cool completely upside down (you can use a few ramekins to prop the cake up by the edge of the tin).

Once cooled, use a knife to release the edges of the cake.

Wrap the cake up in plastic wrap and leave at room temperature if using the the next day. Otherwise, wrap the cake in a second layer of aluminum foil and freeze for up to 3 months.

Sprinkle granulated sugar over the tops of the berries.

Transfer the berries and syrup to a saucepan and heat over medium heat.

In a small bowl, make a slurry with cold water and cornstarch and stir until the cornstarch dissolves.

Once the berries are at a simmer, pour in the cornstarch slurry and cook for 1-2 minutes, stirring until the berries and syrup thicken.

Remove from heat and let cool completely before using.

In a bowl of a stand mixer fitted with the whisk attachment, add in cold heavy cream, vanilla extract and powdered sugar.

Whip until the cream reaches medium peaks - the cream will just start to fall when the whisk is removed. (Note: It's better to underwhip than to overwhip, as it will quickly turn to butter if overwhipped).

Transfer the whipped cream into a large mixing bowl and set aside.

In the same stand mixer bowl, fitted with a paddle attachment, add in softened cream cheese.

Whip until the cream cheese is creamy.

Add in powdered sugar and continue to whip until lightened and fluffy.

Pour in vanilla extract and whip until incorporated.

Working in portions, use a spatula to fold in the whipped cream into the whipped cream cheese to lighten.

Continue to fold in the whipped cream, until all of it is incorporated into the cream cheese mixture.

If not using right away, transfer the cream cheese frosting into an airtight container and store in the fridge.

Split each cake in half equatorially with a sharp, serrated knife.

Dollop a little Chantilly cream cheese frosting onto the cake board.

Place the first cake layer on the cake board.

Spread about ¼ C of frosting onto the cake.

Pipe a border of frosting around the cake edge (using a plain tip).

Add ⅓rd of the cooled mixed berry filling onto the frosting, just until the border.

Place fresh berries sparsely in the layer.

Add another cake layer and repeat, ending with the final cake layer.

Spread the frosting over the entire surface and sides of the cake using an offset spatula (also known as a crumb coat).

Chill the cake in the fridge for 10-15 minutes to let the frosting set.

Add another layer of frosting to cover the cake and decorate with fresh berries.

Chill the cake in the fridge until ready to serve.