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.