Preheat the oven to 400 degrees. Prepare two 9x13 casserole dishes with nonstick cooking spray.
In a dutch oven over medium heat, add the olive oil and onion, cooking about 3 minutes or until softened.
To the onion, stir in the potato, mixed vegetables, seasonings, and butter. Allow the butter to melt.
Sprinkle the flour over the contents of the skillet and stir to combine. Cook about 2 minutes before slowly adding the chicken broth, stirring and scraping the bottom. Reduce the heat to low and allow to bubble for one minute as it thickens. Remove from heat.
In a large (30 quart) bowl, combine the shredded chicken and sauce. Divide evenly between the two casserole dishes.
In a different bowl, stir together the baking mix and milk to make the biscuit batter. Drop the biscuit batter over the casseroles creating and even layer.
Place the skillet in the oven and bake for 15 to 20 minutes or until the biscuits are cooked through and golden..
Allow the chicken pot pie to rest for 5 minutes prior to serving.