Heat oven to 425°F. Soften pie crusts as directed on box. Place one crust in the bottom and up the sides of a 9-inch pie pan.

Heat a large saucepan on the stove over medium heat. Melt butter, then add onions. Cook until onions are softened, 2-3 minutes. Add garlic and cook for 1 minute, then whisk in flour and cook until golden, about 2-3 minutes.

Whisk in chicken broth, then the half and half or milk and bring to a boil. Stirring frequently, simmer until thickened, about 5-6 minutes.

Remove from heat and stir in salt, pepper, diced chicken and vegetables. Pour into the prepared pie pan cover the top with the second crust and pinch the edges closed with your fingers. Cut several slits in the top or pierce holes with a fork to vent.

Bake for 30-40 minutes. Check halfway through - if the edges begin to get too dark, cover just the edges of the crust with foil. Let pie sit for 5-10 minutes before serving.