Amma's is inside Aditi Spice Depot at 600 Carlisle Dr. in Herndon, which is a little shopping strip set back and visible from Elden Street. It offers an Indian vegetarian menu with about 30 items, including chaat and dosa. The chaat are a particular bargain at under $5 each. At least some of them are served in a bowl fashioned from a pappadum and everything is made to order. Even if you order something that is in the hot display case, they make a fresh version for you. I found my aloo tikka chat to be more than enough for a meal by itself.
On our prior visit, we ordered the saag paneer. I'm not sure how they did it, but their version was a much brighter color than most (but not an artificial looking bright), and tasted as if it had not been cooked for quite as long (a good thing). It was very flavorful.
This is an order at the counter, eat at a table or carryout sort of place, open primarily lunchtime hours.