Kosher food is a way of life for the Jewish community. Travelers to this country are restricted by just a few selected establishments that offer this special variety of food. Mumbai is home to some eclectic Jewish communities like the Bene Israeli Community, the oldest and largest Jewish community. This community has adapted to the local flavors of Marathi cuisine. The dishes are redolent with spices. Coconuts and mangoes are staples. Only fish, sheep, goats and certain fowl are eaten – no beef.

So what exactly is kosher food?
Kosher food is food prepared in accordance with Jewish dietary laws.

In their most "biblical" form, Jewish Dietary Laws state:
Pork, rabbit, eagle, owl, catfish, sturgeon, and any shellfish, insect or reptiles are non-kosher. Other species of meat and fowl must be slaughtered in a prescribed manner to be kosher. Meat and dairy products may not be made or consumed together.
A kosher food that is processed or cooked together with a non-kosher food, or any derivative of a non-kosher food, becomes non-kosher. For example, food coloring derived from a shellfish and used in a cake makes the cake non-kosher.

While Jewish Dietary Laws originated in the Bible (Leviticus 11 and Deuteronomy 17), they have been codified and interpreted over the centuries by rabbinical authorities.

Likewise definitions of kosher have evolved in response to changes in the food industry, the Jewish People, and world culture.

Due to the growing complexity of foodstuffs, the need arose for kosher certifying agencies to determine the kosher status of prepared food. Today kosher labels are printed on the packages of kosher food.

In Mumbai Kosher food is hard to come by except perhaps at Jewish homes and The Chabad centre. Hotel Sassoon in Byculla provides Kosher food but "only for guests of the hotel" says Mr. Hayeem who runs the show. "We prepare the food at the owner's house and get it across for guests."
Other than that, there are no other "kosher restaurants" in Mumbai. Having said that, Hindus and Indians in general are very strict about veg/non-veg, so most of the Jewish locals (even most of the Shomer Shabbat, Shomer Kashrut Indian Jews) eat at restaurants that are pure vegetarian and just don't order dishes with cheese.
In Mumbai you'll also find the only Kosher Bakery in India to make strictly kosher products, which is housed on the ground floor of the ORT India building at Worli.