"I don't know what she put in her chicken tetrazzini but Paul looove it."

Preface: Watch this video.

Reduced-fat Chicken Tetrazzini - Cook's Country

12 ounces boneless, skinless chicken breasts, trimmed of all visible fat and cut into 3/4" pieces
2 tablespoons soy sauce
1 slice hearty white sandwich bread, torn into quarters
7 tablespoons grated Parmesan cheese
2 1/4 teaspoons salt
3/4 teaspoon pepper
5 ounces spaghetti, broken in half
2 tablespoons all-purpose flour
1 tablespoon unsalted butter
8 ounces white or cremini mushrooms, trimmed and sliced thin
1 onion, chopped fine
1 cup frozen peas
1 cup low-sodium chicken broth
2 tablespoons dry sherry
2 ounces Neufchatel cream cheese

Combine chicken and soy sauce in zipper-lock bag and refrigerate for 30 minutes to 1 hour. Pulse bread, 2 tablespoons Parmesan, 1/4 teaspoon salt, and 1/4 teaspoon pepper in food processor until finely ground, 8 to 10 pulses.

Meanwhile, adjust oven rack to upper-middle position and heat oven to 400 degrees. Bring 2 quarts water to boil in large saucepan. Add pasta and 1 1/2 teaspoon salt and cook, stirring often, until just al dente. Reserve 1/2 cup cooking water, then drain pasta and return to saucepan. Toast flour in 12" skillet over medium heat, stirring constantly, until just beginning to brown, about 5 minutes. Whisk flour into reserved cooking water; set aside.

Melt butter in now-empty skillet over medium-high heat. Add mushrooms, onion, remaining 1/2 teaspoon salt, and remaining 1/2 teaspoon pepper and cook until browned, 6 to 8 minutes. Stir in peas and add mixture to saucepan with pasta.

Add broth and sherry to now-empty skillet, scrapping up browned bits. Stir in reserved flour mixture, cream cheese and remaining 5 tablespoons Parmesan and bring to boil, whisking until smooth. Add chicken and simmer until exterior of chicken is opaque, about 1 minute. Add chicken mixture to pasta mixture and toss until combined. Scrape into 8" square baking dish and top with bread crumb mixture. Bake until golden brown, 12 to 14 minutes. Let cool on wire rack for 10 minutes. Serve.