This my interpretation of the unlikely condiment offered at felafel stands from Israel to NY. Unlikely because it seems to have roots in a tasty Indian condiment Meth-amba (sp.?) that apparently came to Israel via Iraqi Jews who arrived as refugees. They set up shawarma and felafel stands in the suburbs of Tel Aviv to serve their compatriots the taste of home. I am not sure how Iraqis first came by this preparation--that is the missing link-- but to taste it is to become instantly addicted to its hot/sour/sweet flavor. Israelis love a variety of strong flavors with their felafel: pickled miniature eggplants, cured lemons, hot harissa mixtures, and chopped salads combined with milder techina and hummus make each bite a surprise. Thus this condiment has been enthusiastically embraced as one more yummy addition to the melange of flavors. Israeli versions include garlic and cumin; some recipes use vinegar or sour salt, some are a raw puree. Indian iterations seem to include, simply, asfoetida, fenugreek and mustard seeds. My sources include a recipe by Gil Hovev, from Matanot Mehamitbach (Gifts from the Kitchen) for the Israeli version. Hovev first pickles the mangoes for 4 days, sun-dries them, then cooks them. Vaishali at Happyburp.com provides a more immediate Indian version: Simmer mango and spices together and serve with rice. I added fresh minced hot peppers, lemon juice and sumac for extra heat and tartness and kept things chunky. A day for the raw mangoes to absorb the salt and a day to let the flavors ripen worked well; I omitted the garlic to allow the fruity notes of the mango to be heard.
Serve as a bright condiment for chicken cutlets, mild fish, grilled tofu or a cheese sandwich.
Toss the mango with the salt in a non-reactive bowl. Cover and chill overnight.
The next day, heat a wide pan over medium-low heat. Add oil. When it shimmers, add mustard seeds. When they start to sputter, turn heat quickly to low and add peppers. Stir once--you don't want to scorch the mixture.
Add mango and spices, stirring to incorporate. Add lemon juice. If mixture appears dry stir in water in about 1/4 cup increments. Add brown sugar, stir until melted in.
Cook, stirring, until mango chunks are tender, adding water as needed. Taste for seasoning and adjust.
Remove from heat and allow to cool. Scrape into container(s) and refrigerate.
Allow to cure at least overnight. Use as a condiment for felafel, shawarma, poultry, fish or meat, a cheese sandwich or a lunch of strained Greek yogurt and crisp Scandinavian flatbread if you're feeling multi-national.