I recommend a visit to Lovely Sweet House (934 E. El Camino Real, Sunnyvale, on El Camino just past Wolfe on the right hand side as you come from the north) if you wish to taste good authentic vegetarian North Indian snacks and all kinds of Indian desserts. Hours are 11 AM to 9 PM though they are open later on weekends. Phone: 408-245-6512.
It is a hole in the wall place, rather lacking in ambience and usually with a bad Hindi movie playing on the in-house TV at high volume (they will turn the volume down if you ask nicely). Very inexpensive and the quality is consistently good. You can ask them to cut out the butter (if you are vegan)or make it less spicy. The staff is friendly and more than happy to accommodate your needs. Don't let the interior scare you away, the food more than makes up for it.
Pav Bhaji (mixed vegetable curry served with bread rolls)
Aloo Tikki with Chana - Potato pancakes with curried garbanzo beans
Chana Bhatura - Fried puffy bread with curried garbanzo beans
Their thali (all inclusive lunch or dinner) is great value. The thalis usually have interesting vegetable dishes that you will not find in the run of the mill Indian restaurants (where else can you find curried lotus stems). It comes with your choice of bread and I recommend the cauliflower or radish parathas. The best I have tasted outside of India. The desserts are very good as well (try the kaju barfi or the pista barfi or the rasgollas).
As a point of reference, they are much better than the Chaat House (multiple locations in the Bay Area) or the usual grubby food that you can get at Swagat or Passage to India or Sue's India Kitchen or any of the other Indian places. About the only other good Indian restaurant in the area is Amber in Mountain View.
On a different note, avoid Sarvana Bhavan (South Indian food, near Castro and El Camino in Mountain View). They have managed to cover the terrible triangle. Bad food, miniscule portions and exorbitant prices. If you feel like South India food, your best bet is still the always crowded Udupi Bhavan (976 E.El Camnio Real, Sunnyvale, CA 94087 Ph 408-830-9600).