Sponge Roll Cake:

• unsalted butter or baking spray for greasing and preparing the pan
• 6 large eggs, room temperature whites and yolks separated for optimal fluffiness
• 1 cup (200g) granulated sugar divided equally for egg whites and yolks
• 1 teaspoon pure vanilla extract for a classic vanilla flavor in the sponge
• 1 cup (120g) cake flour, sifted if not using a scale, fluff flour well, scoop, and level with back of knife for accuracy
• ⅓ cup (40g) powdered sugar for dusting the kitchen linen

Preserve Filling & Fresh Berries:

• ½ cup (150g) raspberry preserves I recommend high-quality brands like St. Dalfour or Bonne Maman for best flavor
• 1-2 teaspoons fresh lemon juice optional, if needed for thinning preserves to an easily spreadable consistency
• 2 cups (1 pint; 475mL) cold heavy cream for making the fluffy whipped cream
• 1½ teaspoons pure vanilla extract to flavor the whipped cream
• ¼ cup (24g) powdered sugar to sweeten the whipped cream
• 7-8 ounces strawberries hulled and very thinly sliced for the internal layer
• 3-4 ounces (¾ cup) blueberries for the ‘star’ section of the flag
• 6 ounces raspberries for the red stripes
• 3-4 ounces red cherries optional, pitted and halved, to mix with raspberries for stripes

Prepare and Bake Sponge Cake:

• Preheat your oven to 375°F (190°C) and position an oven rack in the center. Lightly grease a half sheet pan (approximately 18 x 13-inches) with unsalted butter or a baking spray. Carefully line the pan with parchment paper, allowing some overhang on the longer sides to make lifting easier later. Lightly grease the parchment paper once again. Set the prepared pan aside.
  
• In the bowl of a stand mixer fitted with a whisk attachment, place the room-temperature egg whites. Begin whisking on low speed for 30 seconds to 1 minute, until the whites appear light and foamy. Increase the speed to medium-high and slowly and gradually sprinkle in ½ cup (100g) of granulated sugar. Continue beating until the mixture forms medium peaks. This means when you lift the whisk attachment, the peak of the beaten whites should gently tip over but not completely collapse. Carefully transfer this fluffy egg white mixture to a large, clean mixing bowl and set it aside while you prepare the egg yolk mixture.
  
• Wipe the stand mixer bowl clean (a small amount of egg white residue is perfectly fine). Add the egg yolks, the remaining ½ cup (100g) granulated sugar, and the pure vanilla extract to the bowl. Using the whisk attachment, beat this mixture on high speed until it becomes thick, pale yellow, and forms a “ribbony” consistency (when you lift the whisk, the batter should fall back into the bowl in a ribbon-like stream and hold its shape for a few seconds). This usually takes about 3 minutes. Remove the bowl from the stand mixer. Gently incorporate about one-third of the whipped egg whites into the beaten yolk mixture using the whisk attachment to lighten the texture. Then, using a large rubber spatula, carefully fold in the remaining egg whites in two additions, taking care not to deflate the mixture. This gentle folding technique is key to keeping the cake airy.
  
• Sprinkle approximately one-quarter of the sifted cake flour over the batter. Using your large rubber spatula, gently fold it in until just combined. Repeat this process with three more additions until all of the flour has been evenly incorporated, and the batter appears airy and smooth. Be sure to scrape the sides and bottom of the bowl thoroughly to ensure no pockets of dry ingredients remain. Don’t worry if the batter deflates slightly; this is normal. Transfer the prepared batter evenly into the greased and parchment-lined half sheet pan. Using a large offset spatula, spread the batter into a uniform layer, ensuring it fills the entire pan right to the edges.
• Gently transfer the sheet pan to the preheated oven and bake for 10 to 12 minutes, or until the cake is lightly golden in color and springs back when lightly touched. While the cake is baking, lay a clean kitchen linen or tea towel (with the long edge facing you) onto a large, clean working surface. Using a fine-meshed sieve, generously dust the entire linen with the reserved ⅓ cup (40g) powdered sugar. As soon as the cake is removed from the oven, immediately run a thin knife around the edges of the pan to loosen the cake. Using kitchen mitts and with the long edge of the pan facing you, carefully and quickly invert the sheet pan and cake onto the powdered sugar-dusted linen in one swift, confident motion. Allow the cake to cool completely to room temperature – this will take approximately 30-45 minutes – before proceeding with assembly and decoration.
  

Assemble and Decorate Cake:

• Note for Jam Preserves: The consistency of your raspberry preserves is important for smooth spreading. If they are very thick, you may need to thin them down slightly; otherwise, they could tear the delicate cake during spreading. I highly recommend using a touch of fresh lemon juice, as it adds a lovely bright punch, but a small amount of water will also work. Add 1-2 teaspoons of liquid at a time and whisk gently until the preserves are easily spreadable but not watery. Use your best judgment to achieve the right consistency.
• In a thoroughly clean stand mixer bowl (preferably chilled), combine the cold heavy cream, powdered sugar, and vanilla extract. Using the whisk attachment, start whipping on low speed, then gradually increase to medium-high. Continue to beat the cream until it becomes thick and forms medium peaks (be careful not to over-whip, or it will become grainy). Set this luscious whipped cream aside. Using a large serrated knife, precisely cut the cooled sponge cake in half cross-wise to create two perfectly equal-sized rectangular layers. Gently lift one piece and carefully transfer it to a clean, parchment-lined half sheet pan or your chosen serving platter for the assembly process.
• Using an offset spatula, spread roughly half of the thinned raspberry preserve onto the first cake layer in a very thin, even coating. This adds a lovely fruity tang and moisture. Immediately follow with about half of the sweetened whipped cream, spreading it smoothly and evenly until it reaches all edges of the cake.
  
• Now, layer the thinly sliced strawberries over the whipped cream, overlapping them slightly to create a full and visually appealing internal layer that covers the entire surface. Once the strawberries are perfectly placed, carefully set the remaining sponge cake layer directly on top. Finish this second cake layer by spreading on the final layer of raspberry preserves, followed by the remaining whipped cream, ensuring a smooth and even top surface for your flag design.
  
• It’s time to create your patriotic masterpiece! Arrange the blueberries meticulously in the top left corner of the cake to create the ‘star’ portion of the American flag. For a more rustic and appealing look, I personally prefer a generous quantity of blueberries grouped together rather than strictly defined rows. To form the ‘red stripes,’ artfully arrange a delightful mixture of fresh raspberries and any pitted, halved red cherries (if you’ve chosen to use them) in four distinct horizontal rows across the remaining white whipped cream surface. Take your time to make the stripes visually distinct and vibrant.
  
• Prep and Storage Instructions: For optimal convenience and flavor, this Flag Cake can be fully assembled and beautifully decorated 1 to 2 days prior to your serving date. As the cake rests, the flavors gently meld and often enhance. To store, lightly cover the cake with plastic wrap, being careful to tent it slightly so it doesn’t touch and disturb the whipped cream. Keep refrigerated until you are ready to serve. For the best serving experience, remove the cake from the refrigerator and allow it to sit at room temperature for 10 to 15 minutes before slicing and enjoying its delightful layers.

Prep and Storage Notes: 

• This Flag Cake is an excellent make-ahead dessert! You can confidently assemble and decorate it 1 to 2 days before you plan to serve. In fact, allowing it to rest often enhances the depth of its flavors. Lightly cover the cake with plastic wrap, ensuring it does not touch the whipped cream, and store it in the refrigerator.
• For the best texture and taste, remove the cake from the fridge about 10 to 15 minutes before slicing and serving. This allows the sponge to soften slightly and the whipped cream to reach its ideal creamy consistency.