Prepare the roux in a small sauce pot by melting the butter on medium heat. Next add the flour and fully incorporate with the butter, letting it cook for a minute or two.
Slowly add the milk, whisking continuously to avoid lumps. Keep whisking until mixture comes to a simmer. It should thicken enough to coat the back of a wooden spoon. Turn the heat down to low and add the cheese. Season with salt and pepper to taste. You should have a luscious cheesy sauce!
In a small bowl melt 1 Tbsp butter. Add the bread crumbs, parmesan, and parsley. Set aside for topping.
In a baking dish mix the cheese sauce with the cauliflower florets and top with a lid or foil (this will help steam cook the cauliflower). Bake in the oven at 350 degrees for 15 minutes. Remove the lid (add a splash of water if needed) and top with breadcrumb mixture. Return to the oven for 10-15 minutes or until top is browned and cauliflower is cooked through and bubbly.
