# What You'll Need:
→ Pasta
01 - 12 ounces rigatoni or penne
→ Onions
02 - 3 large yellow onions, thinly sliced
03 - 2 tablespoons unsalted butter
04 - 1 tablespoon olive oil
05 - 1/2 teaspoon fine salt
06 - 1/4 teaspoon freshly ground black pepper
07 - 1 teaspoon granulated sugar
08 - 2 cloves garlic, minced
09 - 1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried thyme)
→ Sauce & Assembly
10 - 1/2 cup dry white wine
11 - 2 cups vegetable broth
12 - 2 teaspoons Worcestershire sauce
13 - 1 tablespoon all-purpose flour
14 - 1 cup heavy cream
15 - 1 1/2 cups grated Gruyère cheese, divided
16 - 1/2 cup grated Parmesan cheese
17 - 1 tablespoon chopped fresh parsley (for garnish)
# How To Make It:
01 - Preheat the oven to 400°F. Lightly grease a 9x13-inch baking dish and set aside.
02 - Bring a large pot of salted water to a boil and cook the pasta until just shy of al dente. Drain and reserve.
03 - Heat the butter and olive oil in a large skillet over medium heat. Add the sliced onions, salt, pepper, and sugar. Cook, stirring frequently, until the onions are deeply golden and caramelized, about 25 to 30 minutes.
04 - Stir in the minced garlic and thyme and cook for 1 minute until fragrant.
05 - Sprinkle the flour over the onions and cook 1 minute. Pour in the white wine, scraping up browned bits, and simmer for 2 minutes to reduce slightly.
06 - Add the vegetable broth and Worcestershire sauce, bring to a gentle simmer and cook for 2 to 3 minutes.
07 - Reduce heat to low, stir in the heavy cream and 1 cup of the Gruyère until the cheese melts and the sauce is smooth.
08 - Toss the cooked pasta and the grated Parmesan into the skillet with the sauce until evenly coated.
09 - Transfer the pasta mixture to the prepared baking dish and evenly sprinkle the remaining Gruyère over the top.
10 - Bake for 20 to 25 minutes until the casserole is bubbly and the cheese is golden brown.
11 - Let the dish rest for a few minutes, garnish with chopped parsley, and serve.
