Add the 3/4 cup of butter flavor Crisco and cut in shortening with a fork, 2 knives or pastry cutter until shortening is the size of small peas.
Add water, a tablespoon at a time, and mix with fork until the dough starts to form a ball.
Work dough into one large ball then separate into two.
You can either roll out the dough between 2 sheets of wax paper, or a floured surface. I prefer rolling it out on a floured surface, sprinkling a little flour on top of the crust and my rolling pin, rolling it out until about 1/8 inch thickness
2Preheat oven to 400 degrees. Grease a 9x9x2 inch square baking pan.
3In a large saute pan, melt the butter. Add the onions and celery and saute for 2 minutes, season with salt and pepper. Stir in the flour and cook for about 3-4 minutes for a blond roux. Stir in chicken stock and bring liquid up to a boil. Reduce to a simmer and continue to cook for 4-6 minutes, or until the sauce starts to thicken. Stir in the half and half and continue to cook for 4 minutes. Season with salt and pepper. Stir in the potatoes, carrots, peas and chicken. Mix the filling thoroughly.
4Line the baking pan with one of the crusts. Pour the filling into the prepared pan. Place the top crust of the filling. Carefully tuck the overlapping crust into the pan, forming a thick edge. Crimp the edges of the pan and place on a baking sheet. Place the sheet in the oven and bake for about 25-30 minutes or until the crust is golden brown and crispy. Remove from the oven and cool for 5 minutes before serving.