Homestyle Green Bean Casserole

From the South Beach Diet Cookbook- This is much healthier than the normal version, and I think it tasted better. I think it could have used more seasoning in the sauce, but I put it down here like it is in the book.

1/2 cup buttermilk
1/2 cup whole wheat bread crumbs
1/4 cup ground walnuts
1 onion, cut crosswise into 1/4 inch slices (onion rings)

Preheat oven to 500. Mix bread crumbs and walnuts together. Dip rings in buttermilk first and then bread crumb mixture. Be careful not to keep liquids in the crumbs to the bare minimum. Once it gets wet, the crumbs won't stick to the onions any more. Lay on a baking sheet that was sprayed with cooking spray. Spray onions with cooking spray, and baked for 20ish mins until golden brown.

Meanwhile, saute:
1 onion, chopped
1/2 pound sliced mushrooms
1/2 teaspoon of thyme
1/4 teaspoon salt

Saute until mushrooms release their liquid (about 3 mins). Sprinkle with 1/4 cup whole wehat flour and stir for 1 min. Then, add 3 cups 1% milk and stir constantly for about 3 mins until thick.

Add 1-16 oz bag of frozen green beans. Stir until beans are coated.

Place beans in baking dish (sprayed with cooking spray). Lay onions on top. Baked for 25 mins in a 400 degree oven.