Step 1: Caramelize the Onions

1. Melt the Butter: In a large skillet, heat 2 tablespoons of butter over medium heat until melted.
2. Sauté the Onions: Add the sliced yellow onions to the skillet. Stir to coat the onions in the butter. Continue to cook the onions over medium heat, stirring occasionally, for about 10-12 minutes, until the onions are soft, golden brown, and caramelized. The caramelization process brings out the natural sweetness of the onions and gives the dish its signature French onion flavor.
3. Add the Garlic: Once the onions are nicely caramelized, add the minced garlic to the skillet. Sauté for another 1-2 minutes until fragrant, being careful not to burn the garlic.

Step 2: Prepare the Sauce

1. Add the Flour: Sprinkle the flour over the onions and garlic, and stir to combine. Cooking the flour for about 1 minute helps to eliminate the raw flour taste and thickens the sauce.
2. Add the Broth: Pour in the beef broth (or chicken broth) and bring it to a simmer. Stir constantly, scraping up any browned bits from the bottom of the pan. This adds even more flavor to the sauce.
3. Stir in the Cream: Once the broth has reduced slightly (about 3-4 minutes), add the heavy cream to the pan. Stir until the mixture becomes smooth and creamy.
4. Add the Seasonings: Season the sauce with fresh thyme, salt, black pepper, and Dijon mustard. Stir to combine, and let the sauce simmer for another 5-7 minutes, until it thickens to your desired consistency.

Step 3: Cook the Tortellini

1. Boil the Pasta: While the sauce is simmering, bring a large pot of salted water to a boil. Add the tortellini and cook according to the package instructions, typically about 3-4 minutes for fresh tortellini. If you’re using frozen tortellini, it may take slightly longer.
2. Drain the Pasta: Once the tortellini is cooked, drain it, reserving about 1/2 cup of the cooking water to help loosen the sauce if needed.

Step 4: Combine Tortellini and Sauce

1. Add the Tortellini to the Sauce: Once the sauce has thickened and the tortellini is cooked, add the drained tortellini to the pan with the creamy onion sauce. Stir gently to combine the pasta and sauce, making sure the tortellini is fully coated in the creamy mixture.
2. Adjust Consistency: If the sauce is too thick, add a splash of the reserved pasta water, a tablespoon at a time, until you reach your desired consistency.

Step 5: Serve and Garnish

1. Serve the Dish: Divide the creamy French onion tortellini among serving plates.
2. Top with Cheese: Sprinkle the grated Gruyère cheese over the top of the pasta. The heat from the pasta will melt the cheese, adding an extra layer of flavor.
3. Garnish with Parsley: Finish off the dish with a sprinkle of freshly chopped parsley for a burst of color and freshness.
4. Serve Immediately: Serve the creamy French onion tortellini hot, with extra grated cheese on the side if desired. Enjoy with a side of crusty bread for dipping into the creamy sauce.

Tips for the Perfect Creamy French Onion Tortellini

1. Use Sweet Yellow Onions: For the best caramelization, yellow onions are the ideal choice as they have a natural sweetness that enhances the flavor of the dish. Avoid using red onions or white onions, as they may not caramelize as well and could alter the flavor.
2. Don’t Rush the Caramelization: Caramelizing the onions is the key to this dish’s deep flavor. Be patient and cook them over medium heat until golden and soft. This may take about 12-15 minutes but is well worth the wait.
3. Opt for Fresh Tortellini: If possible, use fresh tortellini for the best texture and flavor. Fresh tortellini cooks quickly and absorbs the creamy sauce better than dry pasta. However, frozen tortellini will also work if fresh isn’t available.
4. Adjust the Creaminess: If you prefer a lighter version of this dish, you can reduce the amount of cream and substitute part of it with milk or even low-fat cream cheese for a tangier twist.
5. Grate Your Own Cheese: While pre-shredded cheese is convenient, it often contains anti-caking agents that can prevent it from melting smoothly. Grating your own Gruyère cheese results in a creamier sauce.
6. Add a Splash of Wine: For extra depth of flavor, consider deglazing the skillet with a splash of dry white wine after caramelizing the onions and garlic. Let the wine reduce before adding the broth and cream.