Fill a medium saucepan ~half full with water. Place over high heat and bring to a boil. Add the carrots, peas, celery, and corn; cook for 10 minutes. Remove from heat and drain. Transfer vegetables into a large bowl; add cooked chicken and stir until well combined. Set aside.

Meanwhile, add the butter to the saucepan. Melt over medium heat the butter. Add onions and garlic; sauté, stirring occasionally, until onions begin to turn translucent (about 6-8 minutes).

Add flour, salt, pepper, chicken broth and milk; stir until well combined. Cook over medium heat, stirring often, until mixture begins to boil. Add vegetables and stir until well combined; remove from heat.

Preheat oven to 425°F.

Pour chicken mixture into casserole dish. (I used an 8”x13” dish, but feel free to use whatever similar size casserole dish you have handy!)

Roll pie crust out so that it is 1” larger than casserole dish on all sides. Place dough on top of chicken mixture. Turn extra dough along edges under itself; flute edges by pinching dough together in regular intervals.

Using a small dish, lightly beat egg with 1 Tbsp of water. Brush top of dough with this egg wash and then sprinkle with Italian seasonings.

Bake at 425°F for 32-35 minutes, or until top is golden brown.