For the Perfect Whipped Cream:
2 cups (454 grams) heavy whipping cream
1 to 2 Tbsp. confectioners’ sugar
1 tsp. vanilla extract
For the cake:
3 Tbsp. all-purpose flour
1 cup (120g) almond flour
3 (150 grams) eggs, at room temperature
1⁄2 cup (100g) superfine sugar, plus 2 tbsp
3 (105 grams) egg whites, at room temperature
1 pinch kosher salt
Confectioners’ sugar for dusting
4 cups (480g) fresh berries
Make the whipped cream:
In a stand mixer fitted with the whisk attachment, combine the cream, confectioners’ sugar, and vanilla and beat on medium speed (you read that right) until just thick—it will start to leave marks from the whisk in the cream.
Remove the bowl from the mixer and, using the whisk attachment, continue whipping by hand for several seconds until the cream reaches the desired consistency; this way, you can ensure the mixer won’t take it too far. Whipped cream is best used right away.
Make the cake:
Preheat the oven to 350°F. Generously grease an 11 by 16-inch jelly-roll pan, then line the bottom with greased parchment paper.
In a large bowl, sift together the all-purpose flour and almond flour. Set aside.
In a stand mixer fitted with the whisk attachment, whip the eggs and 1⁄2 cup sugar on high speed for about 8 minutes. The batter should be very light in color and texture. When you lift the whisk out of the mixture, the batter should form a ribbon that sits on the surface of the egg foam for several seconds. Turn the speed to medium and continue to whip for 1 minute more. Remove the bowl from the mixer and, using the whisk attachment or a rubber spatula, gently fold the almond mixture into the egg foam in three additions.
In a clean mixer bowl with a clean whisk attachment, whip the egg whites and salt on medium speed just until they start to foam. Slowly sprinkle in the remaining 2 Tbsp sugar to create a French meringue, then whip on high speed until glossy, stiff peaks form, 1 to 2 minutes. Remove the bowl from the mixer and, using the whisk attachment or a rubber spatula, gently fold the meringue into the almond batter.
Pour the batter into the prepared pan and spread evenly with an offset spatula.
Bake until the cake is set and just golden on top, 12 to 15 minutes. Let the cake cool completely in the pan.
Dust a clean kitchen towel with confectioners’ sugar. Invert the joconde onto the prepared towel and carefully peel off the parchment paper.
Cover the joconde with half of the whipped cream, then top with half of the berries.
Using the towel to get started, roll the joconde, starting at the short end, into as tight a log as you can manage. Transfer the log to a serving platter. Cover with plastic wrap and refrigerate for 1 hour.
Remove the log from the refrigerator, then top with the remaining whipped cream and berries. Dust with confectioners’ sugar before serving.