Spatchcock the chicken by laying it down on its breast. With a knife or scissors, cut the backbone out. Mash the chicken down to break the breast bone so it will lay flat. Clip the wing tips off.
Pat the chicken down with paper towels to dry well. Generously rub with avocado oil or olive oil. Season well with Mesquite seasoning or seasoning of your choice.
Place on the indirect side of a preheated grill to 240 to 250 degrees F. Cook for about 1 to 1 ½ hours, or until the internal temperature of the chicken is 165 degrees F. Remove and set aside to cool. Shred into bite size pieces.
In a large cast iron skillet, melt the butter over medium heat. Stir in the onions and carrots. Cook for about 8 minutes or until the carrots are tender. Stir in the mushrooms and cook for about 5 minutes, or until the mushrooms are tender. Stir in the garlic.
Sprinkle in the flour and mix well. Cook for 2 to 3 minutes, stirring constantly.
Pour in the broth, heavy cream and thyme. Simmer for about 4 minutes, or until the mixture thickens, stirring occasionally. Season with Original seasoning, or salt and pepper.
Stir in the shredded chicken, corn and parsley. Remove from the heat and set aside.
In a small bowl, whisk together the egg and water.
Place 1 pie crust in a 12-inch cast iron skillet or pan pie pan and top with the chicken mixture. Top with the remaining pie crust and cut several vent holes.
Bake in a preheated oven to 425 degrees F. for 30 to 35 minutes, or until the crust is golden brown.