Rotisserie Chicken Spaghetti Bake

1 . Stage

Heat 3 tablespoons butter in a large, heavy skillet over medium-high heat until foaming subsides. Add mushrooms, 1/2 teaspoon salt, and 1/4 teaspoon pepper; saute until mushrooms turn golden and no liquid remains, about 8 minutes. Remove from the heat and set aside.

2 . Stage

Move an oven rack to the middle position and preheat to 350 degrees F (175 degrees C). Butter a shallow 3-quart glass or ceramic baking dish.

3 . Stage

Melt remaining 3 tablespoons butter in a heavy, 2- to 3-quart saucepan over low heat. Whisk in flour and stir until the mixture becomes paste-like and light golden brown, about 3 minutes. Add stock in a fast stream, whisking constantly, and bring to a boil over medium heat. Reduce heat and simmer, whisking occasionally, until thick and smooth, about 5 minutes. Add cream and vermouth, and season with salt and pepper. Simmer over low heat, whisking occasionally, for 10 minutes.

4 . Stage

Meanwhile, bring a large pot of lightly salted water to a boil. Cook spaghetti in the boiling water, stirring occasionally, until tender yet firm to the bite, about 12 minutes. Drain well.

5 . Stage

Toss drained spaghetti, mushrooms, and 1/2 of the white sauce together in a large bowl, then transfer to the prepared baking dish. Make a depression in the center of the noodles.

6 . Stage

Stir together chicken and remaining sauce in the empty bowl, then spoon into the center of the noodles. Sprinkle with Parmesan cheese.

7 . Stage

Bake in the preheated oven until sauce is bubbling and top is lightly browned, about 30 minutes. Serve immediately.