Yellow Split Pea Soup with Butternut Squash

Heat olive oil in large pot over moderate heat; add onion, carrots, celery (and jalapeno, if using) and saute about 10 minutes til onions are soft and beginning to color. Add garam masala (see note below) and cook, stirring, for a minute or two to toast. Then add stock and split peas. Bring to a simmer, cover partially and adjust heat to maintain a simmer. Cook, stirring occasionally, til peas are tender, about 45 minutes. Adjust water to thin soup if needed. Remove jalapeno. Add squash (see note below), potato and tomatoes with juice. Simmer gently, partly covered, til squash is tender, about 20 minutes. (If you add already roasted squash at end and skip the potato, you can skip this 20 minutes of cooking too.) Stir in cilantro, season with salt and pepper and lemon juice to taste. Serve immediately. (under cook the squash slightly if you make this ahead, so it won''t be overcooked when reheating).