Heat the oven to 150C (130C fan)/300F/gas 2.
In a large bowl, beat the eggs, sugar, cocoa and amaretti to a thick paste, gently stir in the milk, then leave to sit.
Put a 22-24cm baking tin in the oven to heat up (this will help the caramel spread later). Put the three tablespoons of caster sugar for the caramel into a small pan on a medium heat and leave to melt. Once it is liquid, add three teaspoons of water and bubble until it becomes a caramel.
Working quickly, get the warm tin out of oven, pour in the caramel and tilt the tin until it completely covers the base in a thin layer.
Pour the milk mixture into the caramel-lined tin and lift it into a second larger baking tray. Pour cold water into the second tray until it comes halfway up the sides of the bonet tin, then bake for 30 minutes, until the bonet is set (but wobbly).
Lift out and leave to cool.
Run a knife around the edge of the bonet, dip the base of the tin into boiling water, then invert on to a serving plate.
Serve with cream.