Different Thanksgiving Green Bean Casserole

I found this when I was making Thanksgiving dinner a few years ago, and we've made it every time since. Love it...it's not your usual green bean casserole, but if you're not married to the traditional one, this is a nice side dish for that meal or any, really.

Ingredients:
* 2 Tbspn butter
* 2 Tbspn flour
* 1 tsp salt
* 1 tsp white sugar
* 1/4 cup diced onion
* 1 cup sour cream or plain greek yogurt
* 3 (14.5 oz) cans french style green beans, (I use frozen, because I think they're crisper)
* 2 cups shredded cheddar cheese
* 1/2 cup crumbled ritz crackers
* 1 Tbspn butter, melted (for topping)

Directions:
1. Preheat oven to 350.

2. Melt 2 Tbspn butter in a large skillet over medium heat. Stir in the flour until smooth and cook for 1 minute. Stir in the salt, sugar, onion, and sour cream. Add green beans and stir to coat.

3. Transfer the mixture to a 2-1/2 quart casserole dish. Spread the cheddar over the top. In a small bowl, combine the cracker crumbs and remaining butter, sprinkling over the cheese.

4. Bake for 30 minutes in the preheated oven, or until the top is golden and cheese is bubbly.