Saute onion in olive oil in a stock pot until translucent, about 5 minutes. Stir in 1 teaspoon salt. Add celery, carrots, sweet potatoes, tomatoes, ginger, garlic, jalapeno, stock and coconut milk, and bring to a boil. Reduce heat and simmer, covered, until vegetables are very soft (about 1 hour). Puree soup in a blender and put through a food mill or wire strainer. Add agave, lime juice, pepper and salt. Reheat and garnish each bowl with cilantro to serve.