Start by making the cheese sauce. Melt 1/2 cup butter in a
medium saucepan. Whisk in the flour, keeping the heat on low-to-medium so it doesn't burn. Keep whisking as that bubbles a little for a couple of minutes. Slowly add in the milk, whisking continuously and watching it, turning it down if needed so it doesn't burn. It will start to thicken, and if it gets too thick, just add more milk. Whisk in the cheese. Add sea salt and pepper. Turn it down low to keep it warm and whisk occasionally while you make the rest…