How to make
Make your sponge cake mix and divide it into 3 - one white, one with only cocoa - light brown and the third with cocoa and Nutella - the darkest and sweetest.
With spoons, successively put all three mixtures in a checkerboard pattern, until you run out of the mixture. Pour a little extra Nutella on top and make swirls with a stick.
Bake the marble sponge cake for 20 minutes in a preheated oven at 350°F (175°C) with a fan.
For the berry jam, put the fruit and sugar in a saucepan and wait for the jam to reduce, until it leaves a clean mark after running a wooden spoon along the bottom of the saucepan.
To present my marble sponge cake with homemade blueberry and raspberry jam I added some lemon peel, mint leaves and ice cream.
Enjoy!