Step 1: Prepare the Cake

1. Preheat the oven to 350°F (175°C). Line a 10×15-inch sheet pan (jelly roll pan) with parchment paper, covering the sides, and spray with nonstick cooking spray.
2. In a large bowl, whisk together 2 3/4 cups cake flour and 2 teaspoons baking powder. Set aside.
3. In the bowl of a stand mixer with the paddle attachment, cream 1 cup salted butter, 2 1/2 cups granulated sugar, and 2 teaspoons vanilla extract until light and fluffy, about 5 minutes, scraping down the sides as needed.
4. With the mixer on low, add 5 large egg whites one at a time, beating well after each addition.
5. Alternate adding the flour mixture and 1 cup milk: 1/3 flour, 1/2 milk, 1/3 flour, remaining milk, remaining flour. Mix until just combined, scraping down the sides as needed.
6. Pour the batter into the prepared pan and spread evenly. Bake for 28–30 minutes, until a toothpick inserted in the center comes out clean.
7. Cool the cake to room temperature on a wire rack, then chill in the freezer for 10–15 minutes (or refrigerate for 1–2 hours) to firm up for easier handling.

Tip: Chilling the cake makes it easier to transfer or cut without crumbling.

Step 2: Make the Blueberry Topping

1. In a medium saucepan over medium heat, combine 4 cups fresh blueberries, 1/4 cup granulated sugar, 1/4 cup lemon juice, and 2 tablespoons cornstarch.
2. Cook, stirring, until the sugar dissolves, the blueberries break down, and the mixture is thick and bubbly, about 5–7 minutes. Use a fork to mash some blueberries if needed.
3. Remove from heat and stir in the remaining 1/2 cup fresh blueberries. Chill in the refrigerator while preparing the whipped topping.

Tip: Let the topping cool completely to avoid melting the whipped cream.

Step 3: Prepare the Whipped Topping

1. Place the stand mixer bowl and whisk attachment in the freezer for 15 minutes to chill.
2. In the chilled bowl, beat 2 ounces cream cheese and 1/2 cup granulated sugar on medium-high speed until smooth and lump-free.
3. With the mixer off, add 2 cups heavy cream. Mix on medium speed until soft peaks form (peaks droop slightly).
4. Scrape the bowl with a rubber spatula to incorporate all the cream cheese.
5. Mix on medium until stiff peaks form (peaks stand straight up). Add 1/2 teaspoon vanilla extract and a pinch of kosher salt, mixing briefly to combine.
6. Chill the whipped topping until ready to assemble.

Tip: Don’t overmix the cream, or it can turn grainy or butter-like.

Step 4: Assemble the Shortcake

1. Remove the chilled cake from the pan (use the parchment to lift it out) and place on a serving platter or cut into squares for individual servings.
2. Spread or pipe the whipped topping evenly over the cake.
3. Spoon the chilled blueberry topping over the whipped cream, spreading evenly or adding dollops for a rustic look.
4. Serve immediately or chill for up to 1 hour before serving.

Tip: For a fancier look, pipe the whipped topping with a star tip and garnish with extra blueberries or lemon zest.