Nutrition per serving may change if servings are adjusted.
1½ cups low-sodium chicken broth, divided
2 tablespoons all-purpose flour
1 tablespoon olive oil
1 (8 ounce) package sliced cremini mushrooms
1 cup chopped onion
6 cloves garlic, minced
1½ cups frozen carrots and peas (7 oz.)
1 tablespoon chopped fresh sage
1 tablespoon fresh thyme leaves, plus sprigs for garnish
½ teaspoon salt
½ teaspoon ground pepper
1 pound shredded cooked chicken (about 3 cups; see Tip)
1 (7 to 8 ounce) prepared pie crust, thawed if frozen
1 egg white, lightly beaten
Preheat oven to 425°F.
Whisk 1¼ cups broth and flour in a medium bowl; set aside.
Heat oil in a 10-inch cast-iron or oven-safe nonstick skillet over medium-high heat. Add mushrooms; cook until browned, 6 to 8 minutes. Reduce heat to medium. Add onion and garlic; cook until tender, 4 to 6 minutes.
Stir in the remaining ¼ cup broth, scraping up any browned bits. Stir in the reserved broth-flour mixture, peas and carrots, sage, thyme, salt, and pepper. Bring to a boil, stirring constantly. Reduce heat and cook, stirring occasionally, until the vegetables are tender, about 10 minutes. Remove from heat; stir in chicken.
Lay pie crust over the chicken mixture, folding the edges over as needed. Cut four 4-inch slits in the crust to allow steam to escape. Brush with egg white.
Bake until the crust is golden and the filling is bubbly, 20 to 25 minutes. Let cool for 10 minutes before serving. Garnish with thyme sprigs, if desired.
Tip: To poach chicken: Place 4 small boneless, skinless chicken thighs or 2 small boneless, skinless chicken breasts (12 oz. total) in a medium saucepan; cover with cold water. Bring to a boil over medium-high heat. Reduce heat to low, partially cover, and cook until an instant-read thermometer inserted in the thickest part registers 165°F, 12 to 15 minutes. Transfer to a plate and shred into small pieces. Reserve broth for use in another recipeit will keep in the fridge for up to 4 days or in the freezer for up to 3 months.