To about 2 cups of the chicken broth add frozen spinach and bring to a boil over high heat, breaking spinach apart as it thaws. Whirl mixture in a blender until smooth, a portion at a time, then return to pan and add remaining broth. Season soup to taste with curry powder (start with 1 teaspooon) and bring to simmering on high heat, stirring occasionally. Add shelled cooked tiny shrimp. Serve soup in bowls and add sour cream to taste.