Pre-heat the oven to 425° F, and grease a 9x13 baking dish with cooking spray.
Add the potatoes and carrots to a medium saucepan, cover with water, and bring to a rolling boil, cooking 'til softened.
Add the butter to a large skillet, and melt over low to medium heat.
Sauté the onions and celery in the butter 'til softened.
Stir the chicken broth and heavy whipping cream into the onion mixture in the skillet.
In a small mixing bowl, whisk together the flour, sage, salt, and pepper.
Slowly whisk the flour mixture into the creamed mixture, making sure there are no lumps.
Allow the creamed mixture to simmer until it thickens to the right consistency for pot pie; you want it to be almost or about as thick as gravy.
Add the potatoes, carrots, peas, green beans, corn, and shredded chicken to the creamed mixture, combining everything well.
Simmer in the skillet over low to medium heat for about 10 minutes.
Then pour the mixture into a greased 9"x13" baking dish.
To quickly make the biscuits, whisk together the flour, baking powder, and salt.
Using a pastry blender, cut the butter into the flour mixture, 'til it makes fine crumbles.
Make a well in the center of the mixture, and add the milk. Mix together well.
Sprinkle a handful of all-purpose flour on a clean surface. Knead the biscuit dough into the flour, shaping it with your hands. Using a rolling pin, roll the dough out to about a 1-2 inch thickness.
Cut the biscuits out with a biscuit cutter or cup.
Place the biscuits on top of the pot pie in the baking dish.
Bake at 425° F for about 20 minutes, 'or 'til everything is bubbly and the biscuits are golden.
Remove from the oven, and serve while warm.