Mornay Vs Hollandaise Sauce: What's The Difference?

Craving a saucy deep-dive? Today, we're exploring mornay and hollandaise. To properly understand these sauces, you must know the five French mother sauces: béchamel, velouté, espagnole, hollandaise, and sauce tomat. While hollandaise is considered a mother sauce, mornay is an adaptation of classic béchamel.

Both mornay and hollandaise sauces are thick, creamy, pale-hued, and served warm. They also present rich yet fairly neutral flavors, which are comparable enough to serve similar culinary purposes. In fact, mornay is often used as a substitute for hollandaise. Ultimately, the characteristics that make them unique are their ingredients and, subsequently, their respective tastes and weights. Where mornay sauce is all about flour, milk, and cheese, hollandaise is all about egg yolks, butter, and lemon juice.

Mornay is a velvety French cheese sauce, essentially béchamel with the addition of Gruyère. This roux-based beauty is inherently luxurious, bringing a savory cheesy accoutrement to any dish. Hollandaise, by contrast, includes neither flour nor cheese. The sauce hails from Normandy, despite its French name meaning "of Holland." Unlike cheesy, savory mornay, hollandaise tastes like a brighter, less savory béarnaise sauce. Its flavor is rich and butter-forward, balanced by the acidity of the lemon. Hollandaise also often includes a pinch of cayenne pepper, which brings dimensional warmth to this mild, creamy sauce.

Mornay sauce begins with a butter-flour roux, cooked low and slow in a saucepan to thicken into a paste. Then, warm milk is slowly added, followed finally by a generous handful of cheese, which melts to become creamy. For uniform melting, shredded or grated cheese works best. Also, to help loosen up the roux enough to accommodate the cheese, an extra pat of butter might need to be added into the mix, compared to classic béchamel.

Mornay sauce dominantly uses Gruyère cheese plus a sprinkle of parmesan. Swiss cheese, mozzarella, or white cheddar can also be used, but are less common. Some preparations also include subtle aromatics like nutmeg, white pepper, garlic cloves, onion, or bay leaves; the solids, if used, get strained out at the end, leaving the sauce with a uniform creamy consistency.

To serve, versatile mornay sauce can be stirred into sophisticated homemade mac and cheese or blanketed into a casserole like white veggie lasagna. Mornay makes a luscious topping over baked oysters or chicken florentine meatballs, and plays a star role in the French comfort food classic, croque monsieur. A draping of mornay sauce also takes baked chicken, salmon florentine, or steamed spinach to the next level. This sauce can even be made in advance and stored in an airtight container in the fridge to use up to four days later. Still, for optimal texture, enjoy that mornay as soon after making it as possible.

Hollandaise sauce combines egg yolks, butter, an acidic component (typically lemon juice or sometimes vinegar), and often a pinch of white or cayenne pepper. To make it, room-temperature egg yolks and lemon juice are beaten together in a double boiler, heated low and slow, then the melted butter is slowly poured in and stirred constantly while heating until thickened. Any seasonings get whisked in at the end. Beyond cayenne, some preparations also add mustard, browned butter, or herbs into the mix, but these customizations stray from the traditional sauce.

Since hollandaise is an emulsion, the sauce's finicky, temperature-sensitive assembly poses an infamous challenging to home cooks. It's easy to accidentally overcook the egg yolks, resulting in an unpleasant texture. In short, it's easier to make a really good mornay sauce than it is to make a really good hollandaise.

To serve, hollandaise is perhaps best known as the lush blanket over traditional eggs benedict, but it also provides a rich moisture element over grilled asparagus, eggs florentine, and poached fish. Unlike mornay sauce, which can be safely stored in the fridge, hollandaise sauce has a shorter window for safe usage, and should be served soon after making. While mornay's milk, flour, and butter might hold up fine over time, letting egg-yolk-based hollandaise sit for an extended period can be a risky food-safety move (Anthony Bourdain voiced some pretty strong opinions about the matter).