Silky Mornay Sauce with Gruyère & Parmesan

By Sprig Originals ✓ · cooked up in Sprig

Mornay is béchamel's richer sibling: a blond roux and infused milk built into a glossy sauce, then finished off the heat with grated Gruyère, Parmesan and a single egg yolk for body. Done right it coats a spoon like heavy cream, never turns grainy, and never tastes of raw flour. Ladle it over cauliflower, croque monsieur, poached eggs, baked pasta or steamed asparagus.

Ingredients

• 2 cups whole milk
• 1/2 small yellow onion, peeled, left whole
• 1 bay leaf
• 3 whole cloves
• 6 black peppercorns

• 3 tbsp unsalted butter
• 3 tbsp all-purpose flour
• 1/4 cup heavy cream
• 3/4 tsp fine sea salt, plus more to taste
• 1/8 tsp freshly grated nutmeg
• 1 pinch cayenne pepper

• 3 oz Gruyère, finely grated (about 1 packed cup)
• 1 oz Parmigiano-Reggiano, finely grated (about 1/2 cup)
• 1 large egg yolk
• 1 tsp Dijon mustard (optional)
• white pepper, to taste

Instructions

1. Make an onion piqué: pin the bay leaf to the flat side of the onion half with the whole cloves. Put it in a small saucepan with the milk and peppercorns. Warm over medium-low heat until steam rises and small bubbles ring the edge, about 6–8 minutes (do not boil). Kill the heat, cover, and let infuse 10 minutes.
2. While the milk infuses, grate both cheeses on the small holes of a box grater and let them come to room temperature — cold, coarsely grated cheese is the main cause of a grainy Mornay.
3. Melt the butter in a heavy 2-quart saucepan over medium-low heat. Whisk in the flour and cook, whisking constantly, for 2–3 minutes: the paste should loosen, smell faintly like toast, and stay pale blond. Do not let it brown.
4. Strain the infused milk through a fine sieve, discarding the onion and peppercorns. With the roux still over medium-low, add the hot milk in three additions, whisking each one completely smooth before adding the next. It will look thick and pasty at first, then thin out.
5. Bring the sauce to a bare simmer, whisking often and scraping the corners of the pan. Cook 8–10 minutes at a lazy blip, until it thickly coats the back of a spoon and a finger drawn through leaves a clean line. This is what cooks out the raw flour taste — don't rush it.
6. Whisk in the heavy cream, salt, nutmeg and cayenne. Simmer 1 minute more, then pull the pan completely off the heat and let it sit 1 minute so the surface stops bubbling (around 175°F / 80°C is ideal for adding cheese).
7. Add the Gruyère and Parmesan in three handfuls, whisking each one until fully melted and glossy before the next. The sauce should be smooth and satiny, never stringy. If it stiffens too much, whisk in warm milk 1 tablespoon at a time.
8. Temper the yolk: whisk 1/4 cup of the hot sauce into the egg yolk in a small bowl, then scrape the mixture back into the pan and whisk hard for 15 seconds. Return the pan to low heat for no more than 30–45 seconds, whisking constantly, to set the yolk without scrambling it.
9. Whisk in the Dijon if using, then taste and adjust with salt and white pepper. Serve immediately, or press plastic wrap directly onto the surface to prevent a skin and hold in a warm spot (not over direct heat) for up to 30 minutes.

Chef's tips

Nutrition (per serving, estimated)

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