Pub Style Sour Cream and Chives 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 flour3/8 pound onion (about 1 medium), chopped
2 tablespoons vegetable oil
7 cups water1 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 cream1
1/2 cups sour cream

Croutons for garnish if desired Cook potatoes until tender. Set aside. 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. Remove from heat and serve with croutons if desired. Makes about 2 1/2 quarts.