Milk cooked with panela and cinnamon and set firm with cornstarch, with coconut through it. It is not an egg custard: it sets solid enough to cut into squares, and it is what Colombia eats at Christmas with buñuelos.
Colombian natilla is not an English custard and the two get confused constantly. There is no egg in it. It is milk cooked with panela and set with a full cup of cornstarch, which gives something firm enough to cut into squares with a knife, not a pouring cream. If you have made natillas in Spain, this is a different dish under the same name. Dissolve the cornstarch in cold milk, never in the hot pot. That is what the third step is for and it is the difference between a smooth natilla and one with lumps that never come out. Stir it again right before it goes in, because cornstarch settles within a minute. Then stir constantly. A full cup of cornstarch in five cups of milk thickens fast and it catches on the bottom of the pot the moment you stop. The last 8 minutes are what turn it from thick to set. Panela is whole cane sugar in a block and it is what gives natilla its colour and its molasses note. If you substitute, use two cups of white and brown sugar mixed rather than one, which is what a pound of panela actually amounts to. It needs hours in the fridge to set firm, and it is traditionally eaten at Christmas with buñuelos.