Make the crust by placing one cup of flour in a bowl; next, add a teaspoon of salt, then the second cup of flour. Add 5-7 tablespoons of ice water. Cut in the shortening with a pastry blender until the mixture resembles a coarse meal.
Gently press the mixture into a circle, cover with plastic wrap, and refrigerate until ready to use.
Preheat the oven to 400 degrees.
Heat the butter in a large skillet over medium heat. Add the flour, stirring constantly for 1-2 minutes.
Slowly whisk in the milk. Whisk in the chicken broth and cook, whisking occasionally, for a few minutes to thicken.
Add the onion, potatoes, carrots, corn, broccoli florets, and chicken. Season with sea salt and freshly cracked pepper to taste.
Pour the pot pie mixture into a large 9x13-inch baking dish.
Remove the dough from the refrigerator and roll it out. Place the dough on top of the filling, pressing it to the edge of the dish.
Cut 4-5 slits on top of the crust to allow steam to escape.
Place in the oven and bake for 45-55 minutes or until the crust is golden brown.