Preheat the oven to 350°F. Line a 10×15-inch sheet pan (jelly roll pan) with parchment paper, including up the sides. Spray the parchment with nonstick cooking spray.

In a large bowl, whisk together the cake flour and baking powder. Set aside.

In the bowl of a stand mixer with the paddle attachment, cream together butter, sugar, and vanilla extract until light and fluffy, about 5 minutes. Stop to scrape down the sides of the bowl as needed.

With the mixer on the lowest speed, carefully add in egg whites, one at a time, beating well after each addition, stopping to scrape down the sides of the bowl as needed.

With the mixer still on low, add ⅓ of the flour mixture into the creamed mixture, then half the milk, another third of the flour mixture, the remaining milk, and then the remaining flour mixture. Mix just until combined. Stop to scrape down the sides of the bowl as needed.

Pour the batter into the prepared pan and bake for 28-30 minutes, or until a toothpick inserted in the center comes out clean. Allow the cake to cool to room temperature on a wire rack.

After the cake has come to room temperature, transfer it to the freezer to chill for 10-15 minutes, or until firm. You can also place it in the refrigerator for 1-2 hours or overnight (covered). Chilling the cake makes it easier to move.

Before starting, place the bowl and whisk attachment from your stand mixer into the freezer to chill for about 15 minutes. Starting with a cold bowl will help the cream whip up faster and with more volume.

Once chilled, add the cream cheese and sugar to the bowl. Mix on medium-high speed until fully combined and no lumps remain.

With the mixer off, pour in the heavy cream. Resume mixing on medium speed until soft peaks have formed (peaks droop slightly). Stop the mixer.

Using a rubber spatula, scrape the bottom and sides of the bowl to incorporate all of the cream cheese.

With the mixer back on medium speed, mix until stiff peaks have formed. (Stiff peaks refer to the whipped cream peaks that stand straight up and hold their shape firmly.)

Finally, add in the vanilla and a pinch of salt, being careful not to overmix.

Chill until ready to assemble.

Remove the chilled cake from the freezer or refrigerator. Pick up the edges of the parchment and remove the cake from the pan and slide it onto the counter. Slice the cake in half down the middle. You should have two rectangles. Gently place one of the cakes onto a serving plate.

Spread half of the blueberry mixture over one of the halves of the cake. Then, top with ⅓ of the whipped cream cheese topping.