Preparation

1. Prepare a 20 cm springform pan by lining only the bottom with baking paper. Preheat the oven to 170°C (top and bottom heat).
2. Sift the flour and baking powder into a bowl and mix thoroughly.
3. Separate the egg whites from the yolks. Beat the egg whites until lightly stiff, then gradually add the sugar mixed with the vanilla sugar. Add the sugar in small batches, mixing constantly until the mixture is thick and shiny, and the sugar is completely dissolved.
4. Pour the water into the whipped cream and mix briefly. Then, while continuing to mix, add the egg yolks one at a time until a smooth, fluffy mixture forms.
5. Add the dry ingredients in 2–3 additions, gently mixing with a spatula or with a mixer on the lowest speed, just until combined.
6. Pour the batter into the prepared pan and smooth the surface. Bake for approximately 40–45 minutes, until a toothpick inserted into the center of the cake comes out clean.
7. After removing from the oven, gently drop the pan from a height of about 10–15 cm onto a countertop covered with a folded cloth. Then, leave the sponge cake in the pan to cool completely.
8. Remove the sponge cake from the pan only after it has cooled completely. It’s best to bake it a few hours in advance or the day before you plan to use it – this will make it more stable and make it much easier to divide into layers.

Preparation method for crispy sunflower seeds:

1. Cream the softened butter with a mixer until light and fluffy. Add the fudge mixture and mix briefly, just until smooth.
2. Set aside about 150g of the roasted sunflower seeds for decoration. Crush the remaining seeds in a blender or mortar into small pieces and gently fold them into the cream.
3. Evenly spread most of the cream on the first sponge cake layer. It’s easiest to do this in portions, then smooth it out with a spatula.
4. Carefully place the second sponge cake layer on top of the cream and press it down lightly. If necessary, you can lightly moisten it first.
5. Spread a thin layer of the remaining cream over the top of the cake and sprinkle with the reserved crunchy sunflower seeds.
6. Cover the finished cake and refrigerate for at least 4–6 hours to allow the cream to set and the flavors to meld. The sunflower seed cake tastes best well chilled and stays fresh in the refrigerator for about 5 days.