Place split peas in a large bowl. Pour boiling water over the peas and cover by several inches. Soak for at least one hour, or even overnight.

In a large pot, sauté onion in oil until soft and golden. Add squash, carrot, and parsnip and sauté an additional 10–15 minutes. Add chicken soup, soaked split peas, salt, pepper, and cumin. Bring to a boil and lower heat, simmering for at least an hour and a half, or until peas have disintegrated. Add lemon juice and blend with an immersion blender until smooth and creamy.

To serve, ladle hot soup into bowls and top each portion with several fresh spinach leaves, mixing gently. They will wilt slightly from the heat. Add a handful of croutons to each bowl and serve immediately.