Green Bean Casserole from scratch

http://www.foodnetwork.com/recipes/alton-brown/best-ever-green-bean-casserole-recipe/index.html

This was good, but I used arrowroot starch instead of flour and it made the onions stick together and bake strangely. It worked fine as a sauce thickener though. And I left out the panko. So that definitely brought this down a notch. David said it wasn't much better than the green beans plain, but I thought it was still fun and will try it again sometime, maybe without any flour coating the onions.