Place the potatoes and carrots in a large sauté pan or skillet. Fill with cold water, until the vegetables are just covered. Heat over high heat until it comes to a boil.
Melt 2 Tablespoons of the butter in the same pan, then add the onions. Cook until soft, about 5-7 minutes. Add the other 3 Tablespoons of butter and toss until melted.
Stir in the flour, celery seed, salt and pepper. Mix in chicken broth and milk. Simmer over medium heat, until thickened. Pour into the pie plate over the chicken and veggies.
Place the other pie crust over top of the filling, then tuck the edges under the bottom crust and pinch to seal. Brush lightly with egg wash. Slice an "X" in the center of the crust to allow steam during baking. Bake at 400 for 45 minutes.
"This recipe is comical that’s how beyond AMAZING it is. The whole thing is perfection and I can’t thank you enough! Every single person that tries it not only goes back for seconds but also wants the recipe, I honestly think I have shared this link at least 20 times. It is phenomenal"--Jess