At various point in my life, I have been asked to explain things to people, and not just in the capacity as a teacher. I've been asked to explain things about Brooklyn, about subway train travel, about kosher food, about Jewish ritual, about what jazz and ragtime music are, about the rules of baseball, and more. (One of the most difficult is explaining jazz. Go ahead, try it.) Many Jews are asked, at various times in their lives, to explain the meaning (and also justify the existence) of well-known Judaic concepts and rituals such as circumcision, kashrut, the wearing of a sheitel, the Priestly Blessing, and other things. Sometimes we get asked about more obscure things regarding particular people in the Torah or other writings, or about shatnes, and so on.But in New York City, especially in Brooklyn, a lot of us kind of assume that even non-Jews know about basic Judaism 101. At least, very basic, rudimentary, media-darling Judaism 101. Things like what a dreidel is (public school kids all seem to learn the chestnut "I Have a Little Dreidel") and what Rosh HaShanah is ("The Jewish New Year and we get the day off from school too!"). Most New Yorkers link foods such as bagels and challah with Jews, even though nearly everyone else, except for the gluten-free eaters, will indulge in these.So when I was asked about Hanukkah at a local grocery store, I was a bit taken aback. Here is the back story: I had purchased the ingredients for making latkes, for a group of teens to make latkes at my Brooklyn synagogue, the East Midwood Jewish Center. I bought two sacks of potatoes, one bag of sweet potatoes, a bag of yellow onions, eggs, a container of matzoh meal, salt, black pepper, nutmeg and cinnamon. I watched with pride as the teens set to work with the kitchen utensils and food stuffs, but then I realized that I had neglected to buy baking powder! Darn. So I walked to the closest shopping area, a few blocks away on Avenue M. I found the missing ingredient and went to the cashier, to pay for it. I mentioned to the cashier, a middle-aged Asian woman, that I bought this for making potato pancakes for Hanukkah."Oh, Hanukkah," she replied in heavily accented English. "That is your Christmas, right?"Now, I could spent some time explaining the story and meaning of Hanukkah. I could have contrasted it to Christmas. But this would have taken time and effort, time I really didn't have at the moment. So instead, I politely answered "No, it is very different but it's also lots of fun. Thanks! Bye." And I walked back to shul with the missing ingredient, which the kids took hold of and used.Should I have taken the time to give a fuller description of Hanukkah? Did I miss an opportunity to explore interfaith relations? I guess that I did. Hanukkah is not at all "Our Christmas," not one bit, other than the gift-giving aspect. But for all I know, the cashier may not even be a Christian, and if I launched into even a brief talk about Hanukkah, she may not have had a reference point. The Missing Ingredient was more than just a food stuff.