Chicken Pot Pie with Puff Pastry Crust

2 Tbsp. olive oil
2 chicken breasts, cut into 1-inch chunks
3 Tbsp. butter
3 leeks, sliced 1/4 inch thick
3 carrots, peeled and sliced 1/4 inch thick
3 cloves garlic, minced
8 oz. mushrooms, chopped
1/4 c. all purpose flour
3/4 c. milk
3/4 c. chicken broth
1/4 c. chopped flat-leaf parsley
1 tsp. Penzey's Northwoods Seasoning (optional)
1 sheet puff pastry, thawed
cooking spray
salt
pepper

1. Preheat oven to 375 degrees.
2. Heat olive oil over medium-high heat in a large skillet.  Sprinkle the chicken with salt and pepper. Add the chicken and cook, stirring occasionally until chicken is no longer pink. Remove pan from heat and place chicken in baking dish. (I used an 8 X 10 dish. Anything around this size would work.)
3. Heat butter over medium heat in a dutch oven or other large pot.  Saute the leeks and carrots for 10 minutes, stirring occasionally.  
4. Add the chopped garlic and cook for one minute, or until garlic is fragrant.  
5. Add the mushrooms and cook for 5 minutes, or until most of the liquid has evaporated from them.  
6. Stir in the flour and cook for one minute. 
7. Whisk in the milk and broth.  Bring the mixture to a simmer and cook until thickened, about 2 minutes.  Add the seasoning and parsley.  Season to taste with salt and pepper
8. Stir the vegetable mixture in the baking dish with the chicken.
9. Roll out the puff pastry and drape it over the baking dish, so it hangs over the edges by 1/4 inch.
10. Lightly spray the puff pastry with cooking spray.  Cut several slits so steam can escape.
11. Bake for 20-25 minutes, or until the pastry is puffed and golden brown.  Let sit for five minutes, and serve.