First, drain the cans of green beans. In the crockpot add the drained green beans and the cans of cream of mushroom.
Next, add in the Worcestershire sauce and season with salt and pepper. You can always add more later if the casserole is under seasoned.
Place the crockpot on high for 3 hours or low for 6 hours to allow everything to become heated through.
Right before serving make the crispy French onions. In the oven, bake at 350F for 5-7 minutes or until they have become a golden brown color. In the skillet, heat on a medium to low heat browning the onions.
When you are ready to serve add the crispy onions but do not put the lid back on. This will make the onions soggy. Enjoy!