French Onion Baked Spaghetti
Your favorite soup just became your favorite pasta.
Serves6
Prep25 minutes
Cook1 hour
Once the temperature outside starts to dip, I immediately shift into cozy dinner mode. I want rich, comforting flavors, I want a warm bowl of soup, I want baked pastas — I want it all. So I went ahead and took one of my favorite flavors, French onion soup, and applied it to one of my favorite dinner mediums: a bowl of spaghetti.
French onion baked spaghetti has all of the caramelized onion goodness you’d expect from the soup, although I do take a little shortcut. I caramelize the onions for about half the time it would normally take, and then add a little Worcestershire sauce and brown sugar to amp up the caramelized flavor. With my deepest respect to full-blown caramelized onions, in this pasta dish you really can’t tell the difference so why not shave off some time?
The onions are mixed with mushrooms, cream, gooey mozzarella, and nutty Gruyère cheese to make a sauce so cozy, it clings to spaghetti like a hug. Then you tuck the pasta into a baking dish, cover it with a blanket of cheese, and bake until the top is as crispy and delicious as any lasagna.
Why You’ll Love It
- Reduce the time but not the flavor. Cut down on the onion caramelization time with flavor-boosting Worcestershire sauce and brown sugar.
- It’s extremely creamy. Broth and cream mix together with the silky onions for a sauce that perfectly clings to the pasta like a warm hug.
Key Ingredients in French Onion Baked Spaghetti
- Onions: Yellow onions have the right balance of sharpness and sweetness to bring that quintessential French onion soup flavor.
- Mushrooms: Caramelize mushrooms with the onions to add a rich umami flavor.
- Worcestershire sauce: Paired with a little brown sugar, Worcestershire sauce adds an instant boost of depth to the onions that mimics a much longer caramelization time.
- Cheese: A combination of sharp, salty Gruyère and melty, mild mozzarella are the perfect combo for a rich, cheesy pasta with a crispy browned topping.
Helpful Swaps
- Use fish sauce or soy sauce in place of Worcestershire sauce.
- Swap out half of the cremini mushrooms for oyster or shiitake mushrooms.
More Baked Pasta Recipes to Try
French Onion Baked Spaghetti Recipe
Your favorite soup just became your favorite pasta.
Prep time 25 minutes
Cook time 1 hour
Serves 6
Nutritional Info
Ingredients
- 4 tablespoons (1/2 stick)
unsalted butter
- 2 pounds
large yellow onions (2 to 3), halved and thinly sliced (about 5 1/2 cups)
- 1 teaspoon
kosher salt, plus more as needed
- 1/2 teaspoon
freshly ground black pepper
- 8 ounces
baby bella or cremini mushrooms, trimmed and thinly sliced
- 1 pound
dried spaghetti
- 3 cloves
garlic, finely grated or minced
- 2 tablespoons
Worcestershire sauce
- 1 tablespoon
fresh thyme leaves (from 1/4 medium bunch), plus more for garnish if desired
- 2 teaspoons
packed light or dark brown sugar
- 1 cup
dry white wine
- 3 tablespoons
all-purpose flour
- 2 1/2 cups
low-sodium beef broth or vegetable broth
- 1 cup
heavy cream
- 6 ounces
low-moisture mozzarella cheese, shredded (about 1 1/2 cups) and divided
- 6 ounces
Gruyère cheese, shredded (about 1 1/2 cups) and divided
Instructions
Arrange one rack in the top position and a second rack in the middle of the oven. Heat the oven to 375°F. Bring a large pot of heavily salted water to a boil over medium-high heat.
Melt 4 tablespoons unsalted butter in a Dutch oven or large heavy-bottomed pot over medium-high heat. Add 2 pounds thinly sliced large yellow onions, 1 teaspoon kosher salt, and 1/2 teaspoon black pepper. Stir well to combine. Cover and cook undisturbed for 5 minutes.
Uncover the onions and add 8 ounces thinly sliced baby bella mushrooms. Continue to cook, stirring occasionally at first and then more frequently once the onions start to brown, until the onions are a light caramel brown color, 15 to 20 minutes. Reduce the heat as needed if the bottom of the pot is getting too dark. Make sure to scrape the bottom of the pot when stirring.
Meanwhile, add 1 pound dried spaghetti to the boiling water and cook according to package directions for 1 minute less than al dente. Drain.
When the onions are ready, stir in 3 finely grated garlic cloves, 2 tablespoons Worcestershire sauce, 1 tablespoon fresh thyme leaves, and 2 teaspoons packed brown sugar. Cook for 1 minute. Stir in 1 cup dry white wine and scrape up the browned bits from the bottom of the pot. Stir in 3 tablespoons all-purpose flour and cook until well distributed and it smells toasty, about 2 minutes.
Slowly whisk in 2 1/2 cups low-sodium beef broth and 1 cup heavy cream. Bring to a boil, whisking occasionally. Reduce the heat to maintain a simmer and cook, whisking occasionally, until the sauce is slightly thickened, about 5 minutes. Remove the pot from the heat.
Whisk in 4 ounces of the shredded mozzarella cheese and 4 ounces of the shredded Gruyère cheese until completely melted and smooth.
Add the spaghetti and toss until combined. Taste and season with more kosher salt as needed. Transfer to a 9x9- or 9x13-inch broiler-safe baking dish and arrange into an even layer. Sprinkle with the remaining 2 ounces shredded mozzarella and 2 ounces Gruyère cheeses.
Bake on the middle rack until the edges are bubbling and the cheese is melted, about 20 minutes. Move the baking dish to the top rack. Turn the oven onto broil and broil until the cheese is browned, 3 to 4 minutes. Let cool for 5 minutes. Garnish with fresh thyme leaves if desired before cutting into pieces like a lasagna and serving.
Recipe Notes
Make ahead
- Steps 2 to 3 can be completed up to 1 day ahead. Let cool completely, then refrigerate the caramelized onions in an airtight container. Reheat over medium heat before proceeding with Step 5.
- Cover the unbaked, assembled spaghetti with aluminum foil and refrigerate for up to 2 days or freeze for up to 3 months. Thaw in the refrigerator overnight. Bake, still covered, at 350°F until heated through and bubbling around the edges, about 20 minutes. Uncover and bake until the cheese on top is golden brown, 15 to 20 minutes more.
Storage: Refrigerate leftovers in an airtight container for up to 4 days. The baked spaghetti will lose some of its creaminess upon refrigeration. Add a splash of broth or water during reheating to loosen the sauce.