(Almost) Homemade Chicken Pot Pie

1 can (14.5 oz) chicken broth
1/2 teaspoon salt
1/3 teaspoon black pepper
1 to 1 1/2 cups milk (I use 2%)
3 tablespoons butter
1 medium onion chopped
1 cup sliced celery (I omitted before and it still tastes good)
1/3 cup all-purpose flour
2 cups diced, cooked chicken (about two breasts)
2 cups frozen mixed vegetables (broccoli, carrots, & cauliflower combo)
1/2 teaspoon dried thyme leaves
1 teaspoon chopped fresh rosemary or 1/4 dried rosemary
1 tablespoon chopped fresh parsley or 1 teaspoon dried parsley
1 (9 inch) refrigerated pastry crust

Preheat oven to 400'F.

Pour chicken broth, salt, and pepper into a glass measure bowl; add enough milk to equal 2 1/2 cups.

Melt butter in large saucepan over medium heat. Add onion and celery. Cook and stir 3 minutes or until translucent. Stir in flour until well blended. Gradually stir in broth mixture. Cook, stirring constantly, until sauce thickens and boils. Add chicken, vegetables, thyme, rosemary, and parsley. Pour into 1 1/2 quart deep round casserole dish.

Roll out pastry. Cut slits or make cutouts. Place pastry on top of casserole. Roll the edges. Bake about 30 minutes until the crust is golden brown and the filling is bubbling.