1/2 Cup Butter
3/4 Cup Sugar
1 teaspoon Vanilla
2 Egg Yolks
1 cup Cake Flour
1/4 teaspoon Baking Powder
1/4 teaspoon Baking Soda
1/2 teaspoon Kosher Sea Salt
1/2 cup Buttermilk
2 Egg Whites
1/2 cup Sugar
1 teaspoon Vanilla
1 pint Heavy Whipping Cream
1 pound Berries (Strawberries, Black Berries, etc.)
Preheat the oven to 350.
FOR THE CAKE:
Whip together butter and sugar until very light and fluffy.
Whip egg, egg yolks and vanilla into butter mixture until whipped light and fluffy.
Whisk together flour, baking powder, baking soda and salt in a bowl.
Whisk in half of the flour mixture into butter mixture until combined.
Whisk in half of the buttermilk.
Whisk in remaining flour mixture until combined.
Whisk in remaining buttermilk until batter is combined and smooth.
Grease and flour a 9"x13" baking sheet or line with baking parchment.
Pour batter into the prepared pan.
Bake at 350 degrees for about 25-30 minutes, until a toothpick comes out clean on doneness check.
Let cakes rest 5 minutes, then turn out cakes to cool on a cooling rack.
FOR THE Cream Filling:
Fill a medium saucepan with 2-3 inches of water.
Bring water to a boil over high heat. Once boiling, reduce to a simmer.
Combine egg whites and sugar in the metal mixing bowl of a stand mixer (or if not using a stand mixer another metal bowl) and place over the simmering water.
Whisk while heating until the sugar is dissolved and mixture temperature reaches 180 degrees (measure temperature with a candy thermometer, or other kitchen thermometer).
Using a whisk attachment on a stand mixer (or with a hand mixer) whisk egg whites and sugar on high until they double in volume. Mixture will be thick and shiny.
Mix vanilla into the whipped egg whites.
In a separate bowl, beat whipping cream until thick. Beat on medium speed rather than high speed to stabilize the cream. This will take longer, but will ensure the cream is not weepy.
Fold 1/4 of the whipped cream into the egg white mixture to lighten.
Fold in remaining whipped cream.
Cut cake into 2-3 rounds or rectangles.
line the edged of the bottom cake layer with berries (all berries if a 2 layer cake or 1/2 if a 3 layer cake),
fill center with cream mixture and top with second cake layer. If making a 3 layer cake, repeat.
Wrap cake and store refrigerated until serving.
Cake can be unwrapped and dusted with powdered sugar to garnish before serving (or additional macerated berries, whipped cream, etc.)