In a saucepan or small skillet, heat the sugar and 45g of water over medium heat until you obtain a caramel. As soon as its color is golden-amber, add the rest of the cold water to stop the cooking (putting a lid on to avoid splashes).
Immediately pour this caramel into the bottom of a cake tin (mine is 24x11cm). Set aside for later.
Coconut flan
Preheat the oven to 180° traditional heat. In a bowl, beat the eggs. Then add the sweetened condensed milk, whisk everything to have a homogeneous mixture.
Add milk and coconut milk, then mix. Finish by incorporating the vanilla and grated coconut.
Pour this mixture into the mold, over the cooled caramel.
Place this mold in a large baking dish. Fill the dish 3/4 full with boiling water (with a kettle it is practical). Bake for about 50 minutes. The top of the flan should be golden (it's the grated coconut that rises during cooking). Test for doneness using a wooden pick which should come out dry.
Leave to cool out of the bain-marie then place in the refrigerator for at least 4-5 hours. This allows the flan to hold up well when unmolded.
Just before unmolding, place the mold in hot water for 10 minutes to liquefy the caramel. Pass the blade of a knife all around to detach the flan from the mould.
Unmold upside down directly onto the serving platter. The caramel flows on the flan. Optionally, sprinkle with shredded coconut and serve.
Video
Notes
Once cooked and cooled, you can keep this coconut flan for about 5 days in the refrigerator in an airtight container.