- 8 ounces thin spaghetti or vermicelli, broken in half
- 3 cups (12 ounces) chopped or shredded cooked chicken
- 4 tablespoons unsalted butter
- 2 cups (8 ounces) sliced button or cremini mushrooms
- 1/2 cup chopped onion
- 1/2 cup chopped celery
- 3 tablespoons all-purpose flour
- 2 cups low-sodium chicken broth
- 1 cup heavy cream
- 2 tablespoons sherry
- Salt and freshly ground black pepper
- 1 cup (4 ounces) grated Parmesan cheese
- 1/4 cup sliced green olives
- 1/4 cup chopped toasted pecans, for garnish
Arrange an oven rack to the center position and heat the oven to 375 degrees.
Bring a large pot of heavily salted water to a boil over high heat. Stir in the pasta, reduce the heat to medium-high, and cook, uncovered, until just al dente, about 6 minutes. Drain well, shaking to remove excess water, and transfer to a large bowl. Stir in the chicken.
Melt the butter in a large skillet over medium heat. When the butter is foamy, add the mushrooms, onion, and celery and cook, stirring, until soft, 3 to 4 minutes. Reduce the heat to medium-low and add the flour. Cook, stirring, for 1 minute. Whisk in the chicken broth and cook, stirring, until it begins to thicken, 1 to 2 minutes.
Stir in the cream and sherry, season with salt and pepper, and continue to cook, stirring, until the sauce comes just to a boil, about 2 minutes. Remove from the heat and stir in 1/2 cup of the Parmesan, along with the olives. Pour the sauce into the bowl with the chicken and noodles and stir to combine.
Transfer the chicken mixture to a 9- by 13-inch baking dish or a large round casserole. Sprinkle with the remaining 1/2 cup Parmesan. Bake until the casserole is bubbling, 25 to 30 minutes. Let rest for 10 minutes