Make caramel by heating granulated sugar and about 8 tablespoons water in a saucepan until the sugar has completely dissolved. Now turn up the heat and cook until the sugar turns toffee-coloured and caramelises. You will know when it is ready from the colour and smell; be careful not to burn the sugar.
As soon as it reaches this point, quickly pour half the caramel into the base of a 1-litre loaf tin and the other half on to a lightly oiled baking sheet.
Tilt the tin so that all of the base and some of the sides are covered.
Leave this to set. Leave the caramel on the sheet to set too, then crush it to make shards (you’ll use this for decoration later).
Put the milk and cream in a sauce pan and bring up to a simmer. Add the coffee powder, cocoa and chopped chocolate and stir until the chocolate is melted, then immediately remove from the heat.
Using an electric mixer, beat the eggs and golden caster sugar together until fluffy.
Slowly add the warm milk and cream mixture, pouring from a height to cool it as it pours, then add the rum and crushed amaretti and mix well.
Pour this into the loaf tin and stand it in a roasting tin containing enough just-boiled water to come a third to halfway up the sides of the loaf tin.
Bake in the oven for 1 hour. The top should feel set when you touch the centre with your index finger; but it will still tremble slightly.
Remove from the water bath and leave to cool. Cover the top with cling film, put in the fridge and leave for 6 hours to set completely.
Remove the cling film. Run a knife all round the edges, between the bonet and the sides of the tin, and carefully turn out on to a plate.