Classic Mornay Sauce

Ingredients

• 1 1/2 tablespoons unsalted butter
• 1 1/2 tablespoons all-purpose flour
• 1 cup whole milk
• Kosher salt and freshly ground black pepper
• Freshly grated nutmeg, to taste, optional
• 2 ounces finely grated Swiss or Gruyère cheese

Directions

1. Set a small saucepan over medium-high heat and melt the butter, watching that it stays pale rather than browning. Whisk in the flour until you have a smooth paste, then keep it moving until the flour no longer smells raw, about 1 minute.
2. While whisking the whole time, pour in the milk in a narrow, steady stream, or add it a couple of tablespoons at a time. Work the whisk around the edges and bottom of the pan so the sauce stays smooth. It will look quite thick at first, then loosen considerably once all the milk has been mixed in.
3. Cook the sauce, stirring as it heats, until it reaches a simmer and starts to thicken a little. Turn the heat down to low and continue stirring until it is thick enough to cling to the back of a wooden spoon, about 3 minutes.
4. Add salt and pepper, then whisk in nutmeg to taste, if you are using it. If lumps show up, whisk firmly until the sauce smooths out, or use a hand blender or countertop blender for stubborn or larger lumps.
5. With the heat still low, add the cheese in 2 or 3 batches, whisking each portion in while the previous one is just shy of fully melted. Do not let the sauce get too hot once the cheese is added, since excess heat can make it separate. Take the pan off the heat.
6. Use the sauce right away, or lay plastic wrap directly against the surface so a skin does not form and hold it warm until needed. The sauce can also be cooled, transferred to a sealed container, and refrigerated for several days. Warm it back up very gently on the stovetop or in the microwave before using.