Hazelnut filling

Roast the ground hazelnuts at 130–150°C until they develop a pleasant roasted aroma.

Combine the roasted hazelnuts with the sponge cake crumbs, ground cinnamon, and freshly grated lemon zest, mixing until evenly blended.

Bring the water and sugar to a boil. Pour the hot sugar syrup over the hazelnut-cake crumb mixture and blend everything until a smooth, pipeable filling is obtained.

Note
Adding sponge cake crumbs slightly increases moisture absorption and softens the intensity of the hazelnut flavor.

Allow the filling to cool completely, then transfer it to clean, reusable containers with tight-fitting lids. Store covered at 2–5°C.

Before processing, allow the hazelnut filling to come to room temperature until it reaches the desired pipeable consistency. Stir briefly before using.

The hazelnut filling can be prepared in advance and stored in clean, tightly sealed reusable containers for 2–3 weeks at 2–5°C.

For longer storage, freeze the filling. Thaw it in the refrigerator before use, then allow it to come to room temperature until it reaches the desired working consistency.