Preheat oven to 400º.
Bring a saucepan of salted water to a boil. Add frozen vegetables and cook until tender-crisp, 3-5 minutes. Drain and set aside.
In Dutch oven, melt the butter over medium-high heat. Add the chicken and cook, stirring occasionally, until broken apart and thawed.
Add the onion and cook, stirring, until softened, about 2 minutes. Sprinkle in the flour and stir well. Stir in the broth, wine, half-and-half, and parsley and bring to a simmer. Cover, reduce the heat to low, and simmer for 10 minutes.
Stir in the carrots, peas and corn. Season with salt and pepper.
Place one pie crust in bottom of each pie pan. Divide chicken mixture evenly between them, then top each with another pie crust. Take a fork and poke a few holes in the top of each pie, then brush egg yolk and water mixture on top of each pie.
Bake 35-40 minutes or until golden brown on top.