Souper Creamy Veggie Soup

2 teaspoons butter
1 small onion, chopped
1 large potato, peeled, cut into 1/2-inch cubes (1-1/2 cups)
1 can (14-1/2 ounces) chicken broth
1-1/2 cups thinly sliced carrots
2 cups small broccoli florets
1-1/2 teaspoons salt
1/4 teaspoon pepper
1/4 cup all-purpose flour
2-1/2 cups milk

Melt butter in a large saucepan over medium heat. Add onion; cook 5 minutes, stirring occasionally. Add broth, potato and carrots; bring to a boil over high heat. Reduce heat and simmer uncovered for 5 minutes. Add broccoli, salt and pepper; cook 5 minutes longer.
Place flour in a medium bowl. Gradually stir in milk, mixing well. Add milk mixture to soup; bring to a simmer. Simmer uncovered 5 minutes or until vegetables are tender and soup has thickened. Serves 6.