preheat oven to 350F
Using a cast-iron skillet, melt butter and cook chopped onion, celery, and carrots until tender
Mix in the peas, thyme, chopped parsley, and flour until the flour coats all the veggies well and cook for 5 minutes, stirring constantly
Whisk in half and half cream and chicken broth and cook until the sauce has thickened. Season with salt and pepper.
Stir in the cooked chicken and mix well
Top with the refrigerated biscuits and brush them with the beaten egg yolk and water mixture. Bake for 20 to 25 mins until biscuits are golden brown.