A Mousse for the Misbegotten
One would think that if one had spent $30 to have five delicious cherimoyas shipped to one, then one would manage to eat those cherimoyas while they were still at peak level of ripeness, especially given that one's cherimoyas do not all reach said stage of ripeness at the same time. As is so often the case, however, one would be mistaken, and one might come home to find the last two, smallest cherimoyas sitting on one's countertop, alone and forlorn, as if to say, "really, we didn't expect any better from you; we know the other cherimoyas were bigger, and if we had hoped to be eaten when we were at our best, it was only because we were stupid, bad cherimoyas who didn't know our place," and one would then be tempted to throw the cherimoyas directly into the trash, just to teach them a lesson, but one would remember that the cherimoyas had not been expensive and that they probably still had a delicious flavor to offer, so one would -- without exactly apologizing to the cherimoyas since one never wants to encourage drama royalty of any sort -- come up with a way to use the overripe fruit.
It may not shock you to find that I found myself in just such a position about three days ago, or that I let the situation go for another two days until I had a few free moments last night. An overripe cherimoya is not an attractive thing; neither is it easy to deal with, and two overripe cherimoyas are about half as easy to deal with. The flesh will have begun to turn brown, but the seeds will be no easier to remove. The picture you see here is the seeds that I removed from the pulp of the last two cherimoyas, and it really doesn't do justice to either their number or their tenacity. To separate the seeds from the flesh, I cut the cherimoyas in half, scooped the flesh into a bowl with a spoon, mashed the flesh with a potato masher, and then fished through with my fingers to remove the seeds. I am not in any way squeamish about such kitchen activities, and the fruit was at room temperature, so it wasn't unpleasant in the way mixing a meatloaf can be with the frozen fingers and all, but plucking seeds out of a bowl of cherimoya flesh is probably not how I'd choose to spend five minutes, if I were looking for a good time.
The mousse itself, on the other hand, is phenomenal, and ridiculously easy to make, once you've removed the seeds and provided that you have good heavy cream. You could do the same thing with overripe mangos or peaches or apricots, I suppose, but the flavor of the cherimoyas is special, so while you'd have something good, you'd have something very different. When you first cut into overripe cherimoyas, they won't look very appetizing. Fortunately, the finished mousse will be a very pale pink and looks just fine.
Obviously, this preparation is loaded with both fat and calories. Also, it is in the nature of both whipped cream and overripe fruit to be ephemeral, so you have, at most, half a day to eat this, before it separates. If you want something that lasts longer, you'll have to stabilize it with gelatin and/or egg whites. You could do that by separating a few eggs, cooking the egg yolks with the lime juice and sugar to make a custard, beating the egg whites separately, then mixing the custard with the mashed cherimoyas, and folding in the egg whites and whipped cream, separately. I suppose that if you wanted to use gelatin, you could soften it in the lime juice and then fold that into the whipped cream after you'd folded in the cherimoya flesh. I have never had great success using gelatin with whipped cream, but that may be because I haven't ever really tried. I'm pretty sure that you can find directions for various types of stabilized whipped cream in Rose Levy Beranbaum's Cake Bible, though.
Or you can just eat the stuff right after it's made.
2 overripe, smallish cherimoyas
The juice of 2 limes
4 T. turbinado sugar
1 c. heavy cream
Remove the seeds from the cherimoyas. Discard the peels. Put the flesh in a bowl with the lime juice and the sugar. Mash well, until the sugar is dissolved. Taste a bit and add more sugar or lime juice, if necessary. The cherimoya flesh will not and should not reach the consistency of a smooth puree. You want some little bits left.
In a very cold bowl with a very cold whisk attachment, beat the heavy cream until it is very stiff. Fold the cherimoya mixture into it. Eat at once, or refrigerate and eat soon.