1. In a wide skillet, heat oil and saute onions, green onions and potatoes until onions soften. Do not brown.
2. Add vegetable stock and stir well then bring to a boil. Reduce heat and simmer for 15 minutes, until potatoes are soft.
3. Add spinach and stir until leaves wilt, 1/2 minute. Remove from heat immediately -- an important step or you will lose that beautiful brilliant green color. Cool the soup to warm.
4. Puree in batches in the blender or food processor. Add cream and season with salt and pepper.