Traditional Mornay Sauce
This is the backbone of a proper gratin or a well-made croque monsieur. It relies on a steady hand while tempering the cheese into the white base.
Control your temperature.
Keep the cheese finely grated so it melts evenly without needing to boil the sauce. Never let the sauce reach a rolling boil once the cheese has been added.
- Heavy-bottomed saucepan
- Whisk
- Fine grater
What goes in.
- 2 tbspunsalted butter
- 2 tbspall-purpose flour
- 2 cupswhole milk, warmed
- 1/2 cupGruyère cheese, finely grated
- 1/4 cupParmesan cheese, finely grated
- 1 pinchnutmeg
- to tastekosher salt and white pepper
Tempering the Cheese
Remove the saucepan from the burner entirely before stirring in the cheese. Residual heat is all you need to create a smooth, unified emulsion.
The method.
Make the roux
Melt butter in the saucepan over medium-low heat. Add the flour and whisk constantly for 2 minutes. The raw flour smell should disappear, leaving a pale, sandy paste.
Create the Béchamel
Slowly pour in the warm milk while whisking vigorously to prevent lumps. Continue cooking, stirring constantly, until the sauce thickens enough to coat the back of a spoon.
Season
Remove from heat. Stir in the nutmeg, salt, and white pepper.
Incorporate cheese
Add the Gruyère and Parmesan a small handful at a time, whisking until each addition is fully melted and incorporated before adding the next.
Other turns to take.
Sharp Mornay
Replace the Gruyère with aged sharp cheddar for a more aggressive, tangy finish.
Herbed Mornay
Stir in a teaspoon of fresh minced thyme or chives at the very end for a brighter profile.
When it doesn't go to plan.
Warm your milk in a separate pan or the microwave before adding it to the roux to prevent clumping.
If the sauce thickens too much, add an extra tablespoon of warm milk at a time until you reach your desired consistency.
Use white pepper to keep the sauce pristine and free of black flecks.
The ones that keep coming up.
Why is my sauce grainy?
You likely added the cheese while the sauce was still on high heat, which causes the proteins to seize and the fat to separate.
Can I make this ahead of time?
Yes, but it thickens significantly as it cools. Reheat it gently over low heat, adding a splash of milk to thin it back out.
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