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.