-
Preheat your oven to 350 F/180°C. Line the base and sides of a 8x8 inch square cake tin with baking parchment.
-
Break the eggs into a mixing bowl, then add the salt and beat using a freestanding mixer with the whisk attachment until they have more than doubled in size and are pale, aerated and mousse-like. This will take about 5 minutes.
-
Measure the Nutella into a microwave-safe jug and microwave for 40 seconds to 1 minute. Or you can soften it in a heatproof bowl over a saucepan of simmering water for 3 – 4 minutes, stirring occasionally, until warm and slightly runny.
-
Stir the heated Nutella, then pour it in a continuous thin stream into the eggs, whisking as you go, until all the Nutella is combined. This will knock the volume out of the eggs quite a bit, but don't worry about it.
-
Pour this mixture into your prepared cake tin and bake for 17– to 20 minutes, by which time the top will be dry, and the middle tender but set in a slightly jellied.Leave to cool completely in the tin.
-
Once cool, cut it into 16 squares, arrange them on a plate and dust with a little icing sugar pressed through a fine tea strainer or sieve.