Cream of Spinach Soup

Name: Cream of Spinach Soup
Ingredients: 1 cup chopped onion; 2 tablespoons butter; 2 cups chopped fresh spinach, packed, or 1 (10 to 12-ounce) package frozen spinach, thawed; 3 medium potatoes (about 1 pound), peeled and cut into 2-inch chunks; 1 1/2 cups chicken or vegetable broth; 1 1/2 cups water; 2 chicken or vegetable bouillon cubes; 2 cups half and half; 1/2 teaspoon salt; 1/8 teaspoon freshly ground black pepper; 3/4 cup sour cream , plus more for serving, if you like; Chopped chives , for garnish; 1 pinch ground allspice , for garnish