Process orange zest and caster sugar into a fine powder.
Warm milk with the orange sugar mixture in a saucepan until just below simmering.
Remove from heat and let infuse covered for one hour.
Cook granulated sugar with 60ml water in a heavy pan until it becomes dark caramel.
Divide the caramel into four moulds and leave to cool.
Preheat your oven to 150°C.
Beat eggs and yolks together then strain the infused milk into them.
Strain the mixture again to ensure smoothness and remove surface froth.
Ladle the custard into the caramel-lined moulds.
Place moulds in a roasting tin filled three-quarters high with hot water.
Cover loosely with foil and bake for 40 minutes until set with a wobble.
Cool the moulds and chill in the fridge for at least two hours.
Run a knife around the edges to unmould onto shallow dishes.