4 teaspoons kosher or sea salt, divided
5 tablespoons salted butter, divided
1 medium yellow onion, diced
2 medium cloves garlic, minced
4 cups (10 ounces) sliced button mushrooms
1 small red bell pepper, seeded and diced
1/2 teaspoon freshly grated nutmeg
1/2 teaspoon paprika
1 pound egg noodles
3 tablespoons all-purpose flour
2 cups reduced-sodium chicken broth
1/3 cup dry sherry
1/2 cup milk
1/4 cup light cream
1/2 cup Parmesan cheese
2-1/2 cups shredded cooked turkey or chicken breast
Garnish: chopped fresh parsley
Set a large pot of water over high heat and add 2 teaspoons salt. In a large (14-inch) skillet, melt 2 tablespoons butter over medium heat. Add onion, garlic, mushrooms, red pepper, 1 teaspoon salt, nutmeg, and paprika; cook, stirring often, until vegetables soften, 8 to 10 minutes. Reduce heat to medium-low and continue cooking until golden brown, about 10 more minutes. Using a slotted spoon, transfer vegetables to a bowl and set aside.
Once water is boiling, add egg noodles. Cook according to package instructions until tender. Drain and set aside, covered.
Meanwhile, melt remaining butter in skillet over medium heat. Add flour and cook, stirring until mixture looks glossy, about 3 minutes. Add broth and sherry in a slow stream, whisking as you go. Bring to a simmer and cook until thickened, about 3 minutes. Remove from heat and add milk, cream, cheese, and remaining 1 teaspoon salt. Whisk together. Reduce heat to low, return pan to heat, and stir in vegetable mixture and turkey. Serve hot over noodles with a generous sprinkling of parsley.