Preheat the oven to 350°F/177°C and prepare a 9x13 inch sheet pan or casserole dish by spraying the sides with baking spray and lining the bottom with parchment paper.

In a medium bowl, add the flour, baking powder, baking soda and salt. Whisk together and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter at high speed until creamy, about 2 minutes. Add the sugar and cream it together with the butter at medium-high speed until light and fluffy, about 2 minutes, scraping the bowl and paddle at the halfway point. Turn the mixer to low and add the egg whites one at a time, mixing until they are just combined and scraping down the bowl and paddle as needed. Add the vegetable oil and vanilla, increase the mixer speed to high and beat for 1 minute.

Turn the mixer off and add the flour mixture all at once. Mix the ingredients on low speed until just combined, then slowly pour in the buttermilk. Continue mixing at low speed for about 30 seconds, until the batter is uniform and combined. The batter will be slightly thin.

Pour the batter into the prepared cake pan and bake for 28 to 32 minutes. The cake is done when it springs back to the touch and a toothpick inserted into the centers comes out clean or with just a few moist crumbs on it. Let the cake cool completely to room temperature before moving on with the recipe.

In a large bowl or the bowl of a stand mixer using the paddle attachment, combine the mascarpone and cream cheese. Beat on medium speed until smooth and creamy, about 30 seconds. Add the powdered sugar a few spoonfuls at a time, beating on low speed until combined. Once fully incorporated, scrape down the bowl and increase speed to medium, and beat until fluffy, about 30 seconds.

In another large mixing bowl, beat the cream, vanilla, and almond extract on medium speed until stiff peaks form, 2 min. Fold the whipped cream into the mascarpone mixture.

Mix together the berry jam and water. Set aside.

Add the strawberries, blueberries, and raspberries into a medium bowl. Toss together with the lemon juice and zest. Set aside.

Once the white cake is completely cooled, gently remove it from the pan by placing a large cutting board on top of the cake pan and flipping it upside down, then lifting the pan away from the sheet cake. Use a serrated knife or large cake leveler to torte the cake (slice through the center horizontally) and create two equal sized cake layers. Place one of the cake layers back into the pan.

Spread the jam mixture onto the cake layer, then add a layer of chantilly cream frosting. Press the lemon coated berries on top. Place the other white cake layer on top.

To create the design pictured, frost the cake with chantilly cream frosting and use a small spatula to make diagonal swipes in the finish. Prepare a piping bag with Wilton Tip 32 and place the remaining chantilly cream frosting inside, then pipe a braided buttercream border around the edges of the cake (here’s a video that shows the technique). Garnish two opposite corners with fresh berries.