Add some butter slices on top. Cover with foil and bake for 40 minutes. After the 40 minutes remove the foil and broil. I usually do about 5 minutes on broil to create a crispy coating.
– Once it's combined add the half and half and bring to a boil while whisking. It should thicken. Salt and season to taste. If you want a more runny sauce add more half and half.