Mac and Cheese and French Onion Soup Walk Into a Bar...

We're firmly in the age of the culinary mashup, and it's delightful. Bulgogi burritos, ramen burgers, smash burger quesadillas, totchos, Caesared spaghetti, red velvet brownies, and now: French onion soup mac and cheese. Of course, mashups can go wrong (looking at you, chicken noodle soup cough drops), but in the case of this pasta dish, everything is very, very right. We start with all-American mac and cheese—which is certainly comforting but frankly can be a little one dimensional—and zhuzh it up with all the trappings of French onion soup, including buttery caramelized onions, nutty Gruyère, and a crunchy breadcrumb topping. 

While the flavors of mac and cheese are typically pretty straightforward, this recipe, developed by our Birmingham-based test kitchen colleague Julia Levy, is layered with deep, rich flavors. As soon as you set your water to boil for the pasta, you'll begin caramelizing onions—a full pound and a half of them. To speed the cooking admittedly lengthy time it takes to caramelize the onions, Julia has you start by covering the lid in the beginning, then removing it to continue cooking until the onions are very soft and brown.

This initial step of covering the pot traps steam, helping to soften the onions much faster than if the lid is left off. As soon as they're softened, the lid comes off to let that steam escape and the browning begin. Even with this shortcut, the onions will take about 40 minutes to reach the sweet flavor and almost-melting consistency we're looking for. Don't cut the cooking time short—these onions are the star of the show. The good news is that the onions only need to be stirred occasionally, so you can multitask and grate and cube the cheese while the onions cook. Once the onions are browned, dry sherry and fragrant fresh thyme go into the pot to further build those classic French onion soup flavors. 

The cheese sauce is a classic mornay sauce made with a butter-and-flour roux, milk, and cheese, but there's a clever addition to give the dish the beefy flavor of French onion soup: bouillon paste, such as Better Than Bouillon. Bouillon paste adds a concentrated kick of savory beefy flavor without diluting or thinning the sauce the way stock or broth would (plus, we think it'd be a bit much to make homemade beef stock just for a mac and cheese, and we generally find that store-bought beef broth tastes terrible).

Of course cheese is a key component of both mac and cheese and French onion soup, and here we're using the classic French onion topper, Gruyère. Julia tested using a combination of Gruyère and onion Jack, but ultimately decided it was best to just let the Gruyère shine on its own. It's a great melter, so there's no need to add other cheeses for the requisite creaminess and gooeyness of a good mac. In addition to melting Gruyère into the sauce, the recipe also calls for folding cubes of the cheese into the mac and cheese mixture before baking to create little pockets of melty, stretchy cheese throughout. 

The final touch is our nod to the croutons that go on French onion soup: panko breadcrumbs mixed with store-bought crispy fried onions. Then into the oven it goes to bake until bubbly, browned, and crispy on top. This baked mac is substantial enough to serve on its own or with a simple green salad, but it also pairs well with roasted or fried chicken and makes a great centerpiece for a vegetarian plate. Oooh-oui it's good!