In a 6 to 8-quart Dutch oven cook carrots and onion in hot butter until onions are tender. Add broth and rice. Bring to boiling; reduce heat. Simmer, covered, for 45 minutes. Cool slightly. Transfer one-third of the soup at a time to a blender. Cover and blend until smooth. Stir in dill. Season to taste with salt and pepper. Serve immediately or cool for 30 minutes.

To freeze, transfer cooled soup into three 1-1/2- to 2-quart (6 to 8 cup) freezer containers. Seal, label, and freeze up to 2 months.

To reheat frozen soup, transfer soup to a large saucepan. Cook, covered, over medium-low heat for 15 to 20 minutes, until heated through, stirring occasionally. Makes 12 servings ( or three 4-serving portions).

To remove frozen soup from container, dip bottom of container in hot water.