Dried plums (prunes) are always available, but in fresh plum season, you can make these with diced firm-ripe plums. The best type of fresh plum to use would be a so-called prune plum, because its flesh is quite dense and not too wet.
Be sure you use unsweetened cider and not sweetened apple juice. The reduced poaching liquid has a nice natural sweetness, but you can skip the step if you'd like and just serve the pears as is.
To make only 1 serving: Place one halved pear in a small skillet and add apple cider to come about halfway up the sides of the pear. Add 1 or 2 slices of ginger. Cook as directed.
There are tons of hot sauces on the market, but chipotle hot sauce adds an extra dimension of flavor because it's made with smoked chili peppers. It's the smoky flavor that gives this marinade a particularly interesting flavor.
A ripe mango should give slightly to the touch and have a splendid, full aroma. In general, mangoes are most affordable, available, and at their peak of flavor during the late summer months--the very best time of all to make this exotic, cooling first-course soup.
The reason for scraping out the gills of the mushrooms is that they turn into a black, slightly gritty liquid when the mushrooms are cooked. It doesn't harm anything to leave them on, but the dish will be nicer if you scrape them out.