Preheat oven to 400°F.
Melt butter in a large pan over medium heat. Add vegetables and season with 1 tsp of each seasoning.
Cook until softened, then add herbs.
Stir in flour and cook 1 minute.
Gradually add chicken broth, stirring until thickened.
Add chicken, milk, cream, and peas. Add the rest of the seasonings including the salt and pepper if needed.
Transfer filling to a buttered skillet or pie dish. OR you can butter the dish and layer the bottom with some of the puff pastry squares.
Top with puff pastry squares and brush with egg wash.
Bake 45 minutes to 1 hour until bubbling and golden.
Garnish with fresh thyme and serve.