Using a pot, boil to boil the cream, milk and lemon zest. Set aside.
On a separate bowl, mix the eggs, white sugar, cocoa powder, coffee espresso, and rum. Add the mixture to cream and milk, then cook in low heat for 4 minutes; do not boil. Strain and set aside.
Prepare the caramel by heating gently together the water, sugar and lemon. Stir continuously and bring the liquid up to boil until mixture turns into golden color. Set aside, and cautiously pour in a kitchen mould.
Pour the cream and milk mixture gently to the kitchen mould.
Pre-heat oven at 180Celcius. Arrange the kitchen mould in the baking tray with little water. Cook for 40 minutes, or until cooked through.
Remove the tray from the oven, and keep in room temperature until warm. Transfer to a fridge for a minimum of 4 hours before serving.
Serve by gently removing the bonnet from the mould using a kitchen knife. Garnish with whipped cream and coffee ice cream.