In Hong Kong, we are lucky to get mangoes from all over Asia, including Taiwan, the Philippines, Pakistan, and India. It's hard to improve on the sweet, rich flavour and silky texture of a fresh, ripe mango eaten straight from the skin. But years ago, I couldn't resist a bargain and found myself buying an entire case of the fruit. With the mangoes all ripening at the same time, I had far more than I could possibly eat. I needed to find a way to preserve them and this recipe is the result.
I loved it so much that I make mango jam whenever I find good quality, reasonably-priced fruit. Because each variety has its own flavour, don't mix them when making the jam. Buy the mangoes up to a week in advance and ripen them at room temperature. Check the fruit daily and put the ones that ripen early in the fridge.
Apple pectin comes as a powder, and should be mixed with some of the sugar and added to the jam just minutes before you take it from the heat. It gives a gentle "set" that's not rubbery. If you want to use another type of pectin, you'll have to experiment for yourself how much to add.
Lay a mango on a cutting board. Use a serrated knife to slice the mango parallel to the flat seed in the centre of the fruit. Turn the mango over and slice again, so you have two pieces of fruit (with the skin on) and the seed. Scoop the flesh from the skin then cut it into small pieces and scrape away as much flesh as possible from the seed. Repeat with all of the mangoes.
Put the mango flesh into a large bowl and weigh it - one case of mangoes should yield at least 750g (26oz) of fruit. For every 100g (3½oz) of fruit, weigh out 75g (2⅔oz) of sugar and one gram ( ⅕tsp) of powdered apple pectin (put the sugar and pectin in separate bowls). Add all but 100g (3½oz) of the sugar to the mango flesh, mixing it in thoroughly until most of the sugar is dissolved.
Cover the bowl and refrigerate overnight. Thoroughly combine the apple pectin with the reserved sugar then put in an air-tight container and set it aside.
The next day, put the fruit/sugar mixture into your largest, widest pot. Bring the mixture to a boil and stir almost constantly for about five minutes. Turn off the heat and leave for about 30 minutes. Bring the mixture to a boil again and simmer for three minutes, then turn off the heat and leave for 30 minutes.
Wash four to six canning jars and their lids. Rinse the jars with boiling water and invert them on a rack to air-dry. Put the lids in a bowl and add boiling water to cover them.
Turn the heat back on under the pot and bring the mixture to a boil. Cook, stirring frequently, for three minutes. Continue to stir while adding the sugar/pectin mixture in a slow, steady stream. Simmer, stirring constantly, for three minutes, then turn off the heat.
For every 100g (3½oz) of fresh mango flesh you started with, measure out 5ml (1tsp) of fresh lime juice. Stir the lime juice into the pot then ladle the jam into the canning jars. Wipe the rims with a damp cloth then screw on the lids tightly.
Fill a large pot halfway with hot water and put a folded-up kitchen cloth in the base. Put the filled jars on the towel and add more hot water so the jars are submerged by about 1cm (7/16 in). Bring to the boil then lower the heat and simmer for 15 minutes. Remove the jars from the water and cool to room temperature. The boiling water bath should vacuum-seal the jars, which means the jam can be stored at room temperature for at least a year; if you skip this step (or if the jars don't seal), keep the jam in the fridge.
This is delicious on buttered toast, and in jam tarts or mango crepe cake.