Preheat your oven to 180°C (356°F). In a large mixing bowl, whisk 4 room-temperature eggs until they turn pale and fluffy, about 5 minutes. Gradually add 3/4 cup sugar, continuing to whisk until the mixture is light and airy. Gently fold in 1 cup of ground pistachios and 1/2 cup of flour, ensuring all ingredients are well combined. Pour the batter into a greased cake pan and smooth the top.

Place the cake pan in the preheated oven and bake for 20–25 minutes. You'll know it's ready when the cake is golden brown and a toothpick inserted in the center comes out clean. Once baked, remove the cake from the oven and allow it to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.

While the cake cools, prepare the berry syrup. In a saucepan, combine 250 g of cleaned fresh berries and 100 g of sugar. Cook over medium heat, bringing the mixture to a gentle boil. Once boiling, remove the saucepan from heat, allowing the berries to infuse the syrup as they cool. Stir in 1 tablespoon of fresh lemon juice and set aside.

In a mixing bowl, beat 6 egg yolks and 100 g of powdered sugar together until smooth and creamy. Gradually mix in 500 g of room-temperature mascarpone cheese, ensuring there are no lumps. In a separate bowl, whip 4 egg whites until they form stiff peaks. Gently fold the whipped egg whites into the mascarpone mixture, taking care to preserve the airiness.

Once the pistachio sponge has cooled, slice it horizontally to create two even discs. Take the first disc and place it on a serving plate. Generously soak it with the berry syrup, allowing it to absorb the flavors. Spread half of the mascarpone cream over the soaked cake, followed by a layer of the berry syrup-infused berries.

Place the second sponge disc on top, utilizing the remaining mascarpone cream to glaze the top and sides of the cake. Smooth out the cream for an elegant finish. Decorate the cake with any remaining fresh berries, and if desired, add a dusting of powdered sugar for an extra touch.