Mexican Macaroni Casserole

1 tablespoon butter
1/2 cup green onions -- sliced
2 tablespoons cornstarch
1/2 teaspoon ground cumin
1/2 teaspoon salt
14 ounces chicken broth
8 ounces Monterey jack cheese with peppers -- shredded
1/2 cup sour cream
8 ounces rotini -- cooked and drained

In a 2-quart saucepan, melt the butter over a medium heat. Add the onions; cook, stirring, 2 minutes. Stir in the cornstarch, cumin, and salt. Gradually stir in the chicken broth until smooth. Stirring constantly, bring to a boil over a medium heat and boil one minute. Remove from heat. Stir in the cheese until melted. Stir in the sour cream. Pour over the pasta; stir to coat. Spoon into a shallow 2-quart baking dish. Bake at 350 degrees for 15 minutes or until hot and bubbly.