There are three things you need to know about Indian-Chinese food. First, it has as much to do with Chinese food—as served in China—as Chinese-American food. Next, it's all about the sauces: Manchurian, Chili, and so on. And last, if you can't stand the heat, stay out of the restaurant.
Indian-Chinese cuisine was first developed in the Chinatowns of Kolkata, aka Calcutta, about a century ago. Most Kolkata Chinese were Hakka immigrants from Guangdong and Fujian provinces, drawn there by work in the tanneries. According to Peter Lo, a Kolkata Hakka descent and owner of Elmhurst's Tangra Masala, in the early years this was largely a bachelor community—wives were left back home in China. The men ate in large communal eating houses, sharing the table with Indian workers. But the relatively bland Hakka dishes weren't to the taste of the locals, so the cooks began adding Indian spices. Thus Indian-Chinese food was born, in essence Chinese wok cooking with Indian flavors. Over the decades, the tanneries largely disappeared, but the eating houses were transformed into restaurants attracting crowds of Indians. Today, Indian Chinese is ubiquitous, the top "ethnic" food in urban India.
The first Indian-Chinese restaurant appeared in New York around 2001, and today there are a few dozen in the region, many in suburbs with large Indian populations. But to my taste, the best is still Tangra Masala on Grand Avenue in Elmhurst. When newcomers come into his restaurant, Peter Lo's first question for them is: "How do you handle spices?" He can make it mild, but then it wouldn't really be Indian-Chinese. Don't worry, because the heat doesn't really begin until the main course.
The appetizers are usually more to Indian tastes than Chinese. Lollipop chicken ($5.95) is the signature starter, a drumstick whose meat is teased up into a ball at the knee joint, then breaded and deep-fried. Pakoras ($4.95) are essentially fritters, usually chicken, seafood, or paneer (pressed curd cheese), which come with a sweet and spicy dipping sauce. But I would go with the Manchow soup ($3), a variation on hot and sour soup, with the sour replaced by a lot of ginger and crispy noodles on top.
From here, you move on to the main courses—the heat. Here you have to understand the sauces. The two main categories are dry (minimal sauce) or wet (a fuller gravy). The sub-categories are Manchurian, Chili, "Szechwan," spicy garlic, spicy black bean, and sweet and sour. They're all variations on heat, each differentiated by color, amounts of sugar, and ingredients. I suggest ordering your meat, seafood, or vegetables with either the Manchurian or the Chili. The latter is best prepared dry, a molten reddish sauce thick with chili peppers and chopped garlic. Most people order the Manchurian sauce wet. It's not quite as spicy as the Chili but still very tasty, acquiring a greenish hue from abundant chopped cilantro and green chili pepper.
If you want a lesson in cross-cultural diffusion and confusion, try the noodle dishes. Here's the key to the code: Indian Chinese chop suey = American chow mein, while Indian Chinese chow mein = American lo mein. Tangra Masala's "American chop suey" is crispy noodles covered with a mélange of meat and vegetables, then smothered in a sweet and sour sauce. The pile is topped with a fried egg, like a lid to keep in the heat. Instead, I would order chow mein, which actually is a very tasty lo mein.
Finally, you come to dessert. In most Chinese restaurants, the most you can hope for is sliced oranges, watermelon, or a sweet soup. Luckily, the Indians have a serious sweet tooth. There's nothing better for cooling down a fire in the belly than a bowl of cold and creamy kulfi ice cream.