In a large stock pot over medium high heat, combine the sherry and oil. When hot, add onions. Saute, stirring, until soft but not brown. Add celery, carrot and bell pepper; saute 5 more minutes. Add remaining ingredients; bring to a boil. Lower heat and simmer for 15 minutes. Before serving, puree 1 cup of the stew in a blender; add back to the pot. Variation: Serve with crushed corn chips on top.