We met a friend for lunch at Sa Pa, the new Vietnamese quick-serve in the Financial District. We tried the beef pho - beefy broth soup with shredded, tender beef, noodles, shredded Napa cabbage and cilantro, basil, mint, bean sprouts and lime ($11). It hit the spot, and apparently it did for others, too, because there were a lot of bowls on the tables. Next pick? The banh mi. What are your cold weather go tos? Tell us in the comments (617-303-7000).