Preheat the oven to 165°C/325°F.

Heat the milk with the vanilla bean and seeds, lemon zest and orange zest in a saucepan over medium heat until it begins to simmer, then take off the heat and let it infuse for 1 hour.

Melt the caster sugar with water over medium heat in a separate saucepan, stirring occasionally, until it reaches a golden-brown colour.

Once caramelized, carefully pour the caramel into a deep dish pan with a diameter of 24cm, swirling the pan to coat the bottom and sides evenly.

Whisk the eggs and egg yolks until smooth in a mixing bowl, add the sugar, and continue to whisk until well incorporated.

Reheat the infused milk until it just begins to simmer, then immediately remove from the heat and quickly whisk it into the egg mixture to combine.

Pour the custard mixture through a fine-mesh sieve.

Skim off any bubbles and dissipate them carefully with a torch before adding the hot custard into the deep-sided dish over the hardened caramel.

Place the deep-sided dish in a larger baking dish and fill with enough hot water to come halfway up the sides of the dish.

Cover with aluminium foil and poke small holes to allow some of the steam to escape.

Bake the custard for 20-35 minutes or until just set, checking 5 minutes before the end of cooking time; it should still jiggle slightly in the middle.

Remove the dish from the water bath and let it cool to room temperature.

Once cooled, cover the dish with plastic wrap and chill in the refrigerator for at least 12 hours or overnight.

To serve, run a knife around the edge of the dish and invert it onto a plate.