Steamed or grilled, filled with beef or rice and beans, all burritos start with the same round, flat flour tortilla. They probably get their name from an old Spanish saying: "If I had a horse, I would go make my fortune, but I only have a little donkey." In Spanish, the word for "little donkey" is "burrito." Like its animal namesake, the burrito can carry anything: beans, rice, sour cream, cheese, avocados, chicken, beef, pork. You name it. In Sonora, Mexico, their likely birthplace, burritos are small, simple affairs, but over the decades, as burritos made their way north and west to their modern day capital, San Francisco, they grew in size and complexity until they became a great Mexican-American delicacy.