Sour Cream and Chive Potato Soup

1 1/4 pounds russet potatoes, peeled and diced into 1/2-inch squares
3/4 cup (1 1/2 sticks) margarine
3/4 cup flour
3/8 pound onion (about 1 medium), chopped
2 tablespoons vegetable oil
7 cups water
1 bay leaf
2 tablespoons chopped chives
1 tablespoon chicken base
1 teaspoon seasoning salt
1/4 teaspoon black pepper
1/2 teaspoon garlic powder
2 cups 2% milk
1/2 cup half-and-half cream
1 1/2 cups sour cream
Croutons for garnish if desired

Cook potatoes until tender. Set aside.

Prepare roux: Melt margarine in small saucepan over medium heat. Gradually whisk in flour until well combined. Cook over medium heat, stirring often, about 3 to 5 minutes or until mixture turns an almond color and is very creamy. Set aside.

To make soup: In large kettle, saute onion in oil until soft. Add water, bay leaf, chives, chicken base, seasoning salt, pepper and garlic powder. Bring to boil. Whisk in milk and half-and-half, then prepared roux; cook, stirring frequently, until thickened. Add sour cream and potatoes. Simmer until soup reaches 160 degrees. Remove from heat and serve with croutons if desired. Makes about 2 1/2 quarts.