Green Bean Casserole

2 tablespoons butter
2 tablespoons all-purpose flour
1 teaspoon salt
1 teaspoon white sugar
1/2 of an onion, grated
1 cup sour cream
3 (14 1/2 oz) cans French-style green beans, drained
1 sleeve crushed Ritz crackers
2-3 tablespoons butter, melted

Directions:

1. Preheat oven to 350 degrees F (175 degrees C).
2. Melt 2 tablespoons butter in a large skillet over medium heat. Stir in flour until smooth, and cook for one 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. In a small bowl, toss together cracker crumbs and the melted butter before sprinkling over the green beans.
4. Bake for 30 minutes in the preheated oven or until the top is golden and bubbly.