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French Onion Mac and Cheese

Transform a classic soup into an easy, cheesy entrée with this crowd-friendly recipe for French Onion Mac and Cheese.
5 from 18 votes
Prep Time 25 minutes
Cook Time 45 minutes
Total Time 1 hour 10 minutes
Servings 8 servings

Ingredients  

  • 10 Tablespoons unsalted butter, divided
  • 2 small yellow onions, thinly sliced
  • 2 cloves garlic, minced
  • 2 teaspoons fresh thyme leaves, minced
  • 1 bay leaf
  • 1/4 cup dry sherry or white wine
  • 2 teaspoons beef bouillon paste
  • 2 teaspoons Worcestershire sauce
  • 1 pound uncooked pasta shells
  • 4 cups whole milk
  • 1/2 cup all-purpose flour
  • 2 cups shredded sharp cheddar cheese
  • 3 cups shredded mozzarella cheese

Instructions 

  • Melt 2 tablespoons butter in a medium saucepan set over low heat. Add the onions, garlic, thyme, and bay leaf and cook until the onions are caramelized, about 35 minutes. 
  • Increase the heat to high then add the sherry, and cook while scraping up any browned bits, for 1 minute. Add the beef bouillon and Worcestershire sauce and stir to combine. 
  • Remove the mixture from the heat and discard the bay leaf. Set the mixture aside.
  • Bing a large pot of salted water to a boil. Add the pasta and cook until al dente, about 10 minutes. Drain the pasta and set it aside.
  • In a medium saucepan set over medium heat, warm the milk until it is simmering then set it aside.
  • In a large heavy-bottomed stock pot set over medium heat, melt the remaining 8 tablespoons butter. Once the butter has melted, whisk in the flour and cook, whisking constantly, until it turns light brown in color and has a slightly toasted aroma, about 3 minutes.
  • Slowly whisk in the warm milk. Continue whisking constantly to avoid any lumps.
  • Cook the mixture while whisking constantly until it is thick enough to coat the back of a spoon, about 2 minutes.
  • Reduce the heat to medium. Stir in the cheddar and mozzarella cheeses until they are
    melted and the sauce is smooth.
  • Add the pasta, stirring to combine, then fold in the onion mixture and serve.
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