If you want to taste serious Indonesian cuisine in the city, your options are sadly limited. Sure, there's some good food to be had, but such restaurants are few and far between, and are often inconsistent.
I kept hearing whispers from Indonesians, well-fed travelers, and fellow New York food explorers that the city's best Indonesian food can be found at an Indonesian mosque in Astoria, where a bazaar sets up in the warmer months. I haven't eaten broadly enough to know if that's true, but after this weekend's bazaar I can easily say this was the best Indonesian food I've ever had. I ate plenty of "Best X's of My Life," and even more dishes I've never seen or heard of before.
This also may the be the sweetest group of food vendors I've ever encountered. They patiently answered every ignorant question I asked. The bazaar was first and foremost a community event, and despite the pouring rain, smiles went all around, even to visitors like me.
It was hard to get a straight answer about how often the bazaar takes place, but keep an eye out for it again later in the season. One vendor said they happen every two months or so (I've also heard monthly), while others thought this was the only one of the year. Your best bets for updates: the Outer Burroughs board on Chowhound and Dave Cook's Eating in Translation. If you can make it, head there early—11 to 12 is your golden hour before the crowds arrive.
Oh, and the approximate grand total for everything you see here? About $40. It could (and should) have fed 12. Just putting that out there.
Parking lot of the Masjid Al-Hikmah Mosque 48-01 31st Avenue, Astoria, New York, 11103 (map)