Step 1

If making immediately, preheat oven to 350F

Step 2

Cut the broccoli, stems included, into bite sized pieces. Plunge in boiling water for 2-3 minutes exactly, then drain and put in ice water to stop cooking. When cold, drain on a clean kitchen towel.

Step 3

Meanwhile melt the butter in a saucepan and add the flour, stirring to combine. Cook, stirring constantly, for a few minutes, without browning. Slowly add in the half and half, stirring or whiskling constantly, until the mixture thickens. Note: you don't need to bring it to a boil. I usually switch to a silicone spatula at the end to keep the sauce from sticking to the pan or scorching.

Step 4

Remove from heat and let cool for 2 minutes. This is important because you don't want the super hot sauce to cause the cheese to curdle. Add 2 cups of the cheese, and stir gently until it melts and the sauce is smooth. Season with salt to taste.

Step 5

Toss the broccoli with the warm cheese sauce until evenly coated, and then spoon into a baking dish. Top with the remaining cup of cheese. If making immediately, bake for 35-40 minutes, or until the cheese is bubbly and starting to turn golden on top. You can run it under the broiler briefly at the end for some browning if you like.

Step 6

If making ahead, cover tightly with foil and refrigerate. Remove from the fridge and let come to room temperature before baking (about 2 hours.) The baking time will probably be slightly longer for the make ahead casserole.