Meet the Java plum, also known as the Malabar plum, the black plum, in Sanskrit the jambu, in Tamil the naga-pazham or naval pazham, in Hindi the jamun or the jamoon, elsewhere in South East Asia the jambol, jambolan, or Indian blackberry--and finally, botanically (this is significant because that contains the singular clue that inspired this recipe) Syzygium cumini.

The small tree which produces the black plum is native to India, and occupies a special place in Indic cosmologies. Ancient Hindu, Buddhist, and Jain texts divide the world into seven "islands" or "continents," Jambudvipa or the "land of the Jamun trees" being the one where us ordinary humans reside. And since the shape of Jambudvipa is said to be triangular with a blunt end pointing south, it is regarded as referencing what we know today as the Indian subcontinent.

So this little black-on-the-outside, purple-on-the-inside fruit carries the weight of Indic mythology in its fibrous and sweet-astringent flesh. Summer is its season, salt is its most natural companion, and--if you picked up the cue from the jamoon's botanical name--cumin is its other best friend. There is a genre of Indian summer drinks whcih pair salt and cumin as cooling antidotes to the summer's relentless heat. The jal-jeera (literally: cumin water) and the aam panna (a roasted raw mango drink) are the genre's most famous representatives. This got me wondering why our most beloved jamoon wasn't also featured more prominently amongst Indian summer coolers, and set me on a path that resulted in this frozen treat of an answer.

Now, I should say that the traditional Indian response to summer heat is not its opposite, which is ice. Rather, cumin is known to be naturally body-cooling, and refrigeration and ice (it's believed) only end up generating more heat as the body counter-balances the introduction of something ice-cold to re-establish a normal body temperature equilibrium. But every once in a good while, there really is nothing like a popsicle, a slushie, a granita, a sorbet, or some other lovely frozen treat, right? Hey, we've another genre of chilled drink in India known as the "sharbat" (mispronounced sometimes as "sherbert")! So, read on for instructions on how you could well just end up with a wonderfully light and naturally cooling sharbat -- or that extra special frozen one.

And last but not least, if you like this instructable, please drop a vote in the "Frozen Treats" challenge, and feel free to leave a comment. Thank you!

Supplies

For sweet-salt black plum ices, you'll need:

black plums or jamoons (available at local grocers and markets in summer months)
sugar
rock salt or table salt
black salt, or kala namak
cumin or jeera seeds
limes

Step 1: Prepare the Black Plum or Jamoon Concentrate

To prepare the syrup or jamoon concentrate, you'll need:

1 kg/ 2-3 quarts fresh jamoon fruits (available from local markets or groceries in summer months)
1 1/2 – 2 cups of sugar, or to taste
1 heaped teaspoon rock salt or regular table salt, or to taste
1/2 teaspoon black salt or kala namak (also available at Indian grocers; optional but imparts an excellent flavor)

Here's the process:

Place as many jamoon fruits as you have in a heavy pan, and add water to cover.
Bring to a boil, reduce heat, and allow the fruit to cook. Use a wooden spoon to mash the fruit from time to time. When it seems that the fruit is mashing easily (about 15-20 minutes), turn off the heat and allow to cool.
Once the mix is cool enough to handle, strain the liquid out, using as large a strainer as you can find. Much of the juice will remain in the fruit pulp, so use a spoon to mash and press the fruit as much as possible to extract the pulpy juice. Stop when it seems like the fruit is getting dry and the jamoon pits are appearing more and more in the left-over pulp.
Now measure out the liquid you have into a pan that can be set on the stove. Add sugar in a 2 cups liquid-to 1 cup sugar proportion, along with half of each type of salt. Bring to a gentle boil until the sugar and salt are incorporated.
Taste at this point — and adjust the sugar and salt, adding what remains or letting it be. You want a mixture that is slightly on the sweeter side, and just a touch salty. A lot of this will depend on the quality and taste of the jamoon fruits, so it's okay to add a bit at a time.
Continue boiling on medium heat for approximately another 10 minutes. Then turn off the heat, allow the liquid to cool, and bottle.
You can stop here and store this concentrate refrigerated, if you wish, for up to a week. Or just refrigerate the concentrate for at least 8 hours and proceed to the next step! (You can see what the concentrate looks like when poured into glasses from the images.)

Step 2: Ice It, Blend It, Serve It!

For this stage you'll need:

Ice! Lots of ice. About 1 cup of ice for a 1/4 cup of jamoon concentrate.
A large blender jar
1 heaped teaspoon cumin or jeera seeds, roasted and lightly crushed in a mortar and pestle, to serve.
1 lime, juiced
1 lime sliced or cut into wedges to serve.

Here's what you do:

First, prep your serving glasses: place a mix of salt and roasted-crushed cumin in small dishes in which you can overturn your serving glasses. Run a slice of lime around the edge of each glass, and dip the rims into the salt-cumin mixture until the rims are nicely coated. Set aside.
For each 1/4 cup of concentrate, add 1 cup of ice and a 1/4 of your juiced lime, along with a few generous pinches of the roasted-crushed cumin seeds. Blend until you've got a thick slushie-smoothie going.
Spoon or pour this carefully into your prepared glasses, taking care not to disturb the rims.
Serve garnished with an additional slice of lime. Et voila!
NOTE: if you want to skip the ice entirely, you can always just add a bit of concentrate (and a crushed jamoon fruit, if you have any left) to a prepped glass, and fill with cool water or even soda. Enjoy!

If you liked this instructable please drop a vote in the "Frozen Treats" challenge. Thank you!