Sponge cakes are often made in Croatia, especially in the continental parts of the country. The thing about sponge rolls is that they look very pretty and are simple to make. There are several key steps to keep in mind while rolling the sponge – and you need to have a foolproof recipe, of course.
In Croatia sponge roll cakes used to be made by grandmothers with just a few modest ingredients and without lavish creamy fillings. The sponge was covered in homemade jam, rolled and sometimes dusted with powdered sugar. Today, modern recipes call for cooking the filling with milk, butter and sometimes eggs, and some even use mascarpone. Simple versions are still being made, usually during weekends and enjoyed with a cup of afternoon coffee. Rich fillings are reserved for special occasions and holidays.
Sponge cakes are not science. As long as you don’t over-bake your roll and remember to roll it up while it’s still hot from the pan, everything will work out just fine.
The eggs and sugar should be whisked for a full 10 minutes with an electric whisk, until pale and thick. It is thick enough when it is about three times the volume. When you lift out the whisk, the thick mixture that drips off should leave a trail on top of the rest.
It is crucial to fold in the flour with a sure but light touch – you do not want to undo all that good whisking by knocking out the air. The tablespoon of water is a breeze to fold in and simply loosens the mixture to help it flow evenly into the corners of the tin (you may need to help it with the spatula).
Baking takes 10-12 minutes, then it is time for rolling up the warm sponge. Once it’s been turned out of its tin onto the sugared paper, trim off the stiff edges, which would cause it to crack during rolling. Use the best jam you can get (preferably homemade). When rolling up the sponge, use the paper to help you roll. Then unroll the cold sponge carefully, spread the filling evenly and re-roll.
Here is a recipe for the chocolate sponge:
150 grams sugar
1 tbsp cocoa powder
3 tbsp all-purpose flour
Separate egg yolks from egg whites. Whisk egg yolks with sugar for 10 minutes, until pale and thick. Add sifted cocoa powder and flour. Whisk egg whites until thick. Add to the egg yolk mixture using your spatula. Don’t mix with electric mixer.
Evenly spread the mixture onto baking sheet (size 35 x 40 cm) lined with parchment paper. Bake for 25 minutes on 180 °C. While still hot, roll baked sponge together with the parchment paper and let cool. Then roll it out, cover with desired filling and roll back again. Let cool in the fridge for at least 2 hours. Dust with powdered sugar, cut into slices and serve.