When you travel to countries with completely different climates than the ones you've known, you are likely to be faced with some weird fruits (and vegetables) that you have no idea how to deal with - or even if they are, in fact, fruits at all. These were such for me. I first saw them in Thailand and so for a long time knew them only by their Thai name, noy-nah; I now know that they are called custard apples in English, and that their botanical name is Annona reticulata.
I could at least identify custard apples as likely fruits from their placement among the pyramidal displays of mangoes, rambutans, and papayas at the front of my local fruit store, but they looked unlikely candidates for deliciousness. They appeared to me akin to rotting artichokes, being of a similar size and shape and covered with bumpy greenish, slightly bruised-looking, conical reticulated protruberances. And just as artichoke consumption is not intuitively obvious, so it is with the custard apple: how do you go about actually eating one of these things, should you so desire? As with so much, a Thai friend had to show me.
The custard apple is a compound fruit, and beneath each protuberance is a segment of cream-coloured flesh that usually contains a hard shiny black seed. The flesh is delicious and sweet with a custard-like texture, though sometimes slightly grainy. The simplest way I found to eat them is to push off the skin with your finger - each protuberance comes off quite easily - and then just eat the fruit out of hand; it's not very juicy and won't run all over your face. Or you can easily break it in two by pressing your thumbs into the indentation at the bottom of the fruit where the stem was, and then eating the fruit with a spoon. In either case you'll get a mouthful of seeds - each fruit can contain upwards of 50; although the seeds are toxic, they're so hard that they will be harmless if ingested whole, but I usually spit them out. The flesh can be used in ice cream and other desserts.
I had assumed that the custard apple was a native of Asia, but recently discovered that it's thought to originate in the West Indies. From there it spread to South America and then Africa and Southeast Asia; it apparently likes cooler tropical climates and has an advantage over other Annonae in that it ripens a little later in the year. Though it seems to be considered by fruit snobs as inferior to its close relative, the cherimoya, I quickly came to love these fruits (along with pomelo, another new one for me) and ate them every day when they were in season.