There are a few specific steps involved in making French onion green bean casserole. You will first need to caramelize the onions in a large skillet. When caramelizing onions, stir every few minutes but only once the onions start to brown. If you continuously stir them, they will never caramelize. On the other hand, make sure they don't burn!
During cooking, you can add a few drops of water to loosen the fond on the bottom of the pan. Brown sugar will help a bit with the caramelization process. Next, you need to make a béchamel or, as it's called here, a white sauce. This creamy delicious sauce will help hold the casserole together. For this step, you will need a sauce pot. Combine everything in a casserole dish, top with breadcrumbs and cheese, and you are ready to bake.