Mix 2 tbsp of the butter with the flour and put aside

In a separate bowl, dissolve the cornstarch in the milk and set this aside

Using a large cast iron pan, cook the onion and celery in the 4 tbsp. of butter and season with salt and pepper to your taste

Add the potato and the broth and bring to a boil, then cover and cook for 10 minutes.

Add the butter/flour mixture and stir this in.

When the mixture has started to boil again, remove it from the heat source and stir in the milk & cornstarch.

Put the pan back on the stove and bring it to a boil once again, then remove it from the heat and stir in the peas & carrots and the chicken.

Cover with a lid to cool while you get your puff pastry ready!

Preheat your oven to 400°F/200°C with the top rack in the lowest position. This is also known as the bottom third of your oven.

Following the package instructions unroll one sheets of puff pastry.

Make sure the cooled chicken mixture is mounding slightly in the middle of the skillet.

Place the  sheet of puff pastry on the top, and cut a few of vents into the top crust with a knife. This will allow the steam to escape and also will make your crust very flaky!

Crimp the edges of your puff pastry around the edge of the cast iron pan  and brush the entire top crust and edges with milk

Bake for 50 minutes, the let cool for about 20 minutes before serving

Yum!