Hot milk sponge cake with cocoa and Balsamic Vinegar of Modena PGI

Ingredients
120g whole milk, fresh
60g butter
145g weak flour
20g bitter cocoa
6g baking powder
165g sugar
1 teaspoon of Balsamic Vinegar of Modena PGI
3 medium size eggs at room temperature
1 teaspoon of vanilla extract
a pinch of salt
Icing sugar and fruit as decoration
Preparation
Author: Imma Di Domenica
Sift twice the flour with the baking powder, the cocoa and salt, then set aside. Pour the milk and the butter in a small pot and warm up until the butter is completely melted. Whip the eggs in a planetary mixer (or with an electric whip) for about a minute at medium-high speed, add the sugar a little at a time and whip until tripled in volume and the mix will look clear-coloured and fluffy (about 10 minutes). With the aid of a spatula, in three times with movements from bottom to top, delicately fold into the whipped mixture the flour, the cocoa and the sifted baking powder . Heat up again the milk and butter, before boiling point pour into the mixture in two times along with a teaspoon of Balsamic Vinegar of Modena PGI and fold with the spatula. Pour into a 22 cm mould lined with baking paper and cook in a preheated oven at 175°C for 25-30 minutes.