Bake puff pastry shells according to package directions. (For best flavor and freshness, bake just before serving.)
In a medium saucepan, melt butter over medium heat. Add onion and celery, cooking until vegetables are tender, stirring frequently, 3 to 5 minutes. (Reduce heat if vegetables start to brown.) Stir in mushrooms and cook until tender, approximately 2 minutes. Stir in flour. Cook, stirring constantly, creating a roux, 1 to 2 minutes. Stir in chicken broth. Cook, stirring constantly, until mixture comes to a simmer. (Mixture will be smooth and creamy.) Stir in cream, soy sauce, poultry seasoning, salt, and pepper until incorporated. Add chicken, peas, and pimientos. Cook over low heat, stirring frequently, until mixture gently simmers and is heated through. Cover pan and keep on very low heat until ready to fill pastry shells.
Place baked pastry shells on a serving dish. Fill pastry shells with warm chicken mixture and sprinkle with Paprika Panko Crumbs. Serve immediately.
Notes
Make-Ahead Tip: Once cooked, chicken filling can be cooled, transferred to a covered container, and refrigerated for up to a day in advance. To reheat, warm chicken filling in a covered saucepan over very low heat. Stir in additional chicken broth to loosen mixture, if necessary.
Recipe by TeaTime Magazine at https://teatimemagazine.com/chicken-la-king-patty-shells/