1.Saute the onions with the butter in the bottom of a heavy, large saucepan over low heat until soft. 2.Sprinkle in the flour; stir and cook 2-3 minutes. 3.Gradually add the chicken broth whisking thoroughly, then the pumpkin puree, and cook gently about 15 minutes. 4. Use an immersion blender, regular blender, or blender to puree the soup. 5. Pour back into the pot, heat and salt and pepper to taste