Diabetic Asparagus Soup Recipe?

In one teaspoon of oil and one teaspoon of butter saute half of a medium size onion until just tender. Add two small cans or one quart on low sodium chicken stock. Add the chopped lower 1/2 ends of one pound of asparagras. Cook until tender. Add remainder of asparagras and cook 10-15 minutes. Cool, then puree in small batches in blender. Reheat and serve. If you like you can add a small amount of half and half to servings.