2 cups sour cream and onion potato chips (roughly crushed)
Preheat oven to 350F, and lightly spray a 1 1/2 quart casserole dish with cooking spray.
In a large skillet over medium heat cook the onions in the butter until soft and lightly browned.
Whisk in the flour and continue cooking until flour is lightly browned. Mix in the chicken broth, half and half, salt, pepper, and thyme. Bring the mixture to a boil, reduce heat to low, and continue cooking until mixture is thickened. Remove from heat, add cheese, and stir constantly until melted.
Mix the hash browns into the cheese mixture and cook over low heat, stirring occasionally until hash browns are thawed, and then mix in the sour cream.
Spoon the mixture into the casserole dish, top with the chips, and bake for 35 to 50 minutes or until hash brown is done, and the top is nicely browned.