1. Bring a large pot of salted water to a boil over high heat. Add the pasta and cook according to the package directions until al dente. Drain and set aside, reserving some pasta water.

2. In the empty pasta pot or a separate saucepan, melt 2 tablespoons of butter over medium heat. Whisk in the flour and cook for about 1 minute, stirring constantly, until bubbly and smooth.

3. Gradually whisk in the heavy cream. Add the Boursin cheese and grated white cheddar, stirring gently until melted and smooth.

4. If the sauce is too thick, add up to 1/2 cup milk until you reach a creamy consistency. Season with salt to taste.

5. Add the cooked pasta to the sauce and stir until fully coated. Add reserved pasta water or more milk if needed to loosen the sauce.

6. In a small skillet, melt 2 tablespoons of butter over medium heat. Add breadcrumbs and toast, stirring frequently, until golden brown and fragrant, about 2–3 minutes.

7. Transfer mac and cheese to serving bowls or a large dish. Sprinkle toasted breadcrumbs over the top. Serve hot and garnish with fresh parsley if desired.