IF USING COOKED MEAT SEE NOTES
Mix the seasoned flour ingredients in a plastic storage bag.
Heat oil in a small (4 qt) dutch oven or very deep skillet over medium heat.
Dredge meat in seasoned flour and place in the heated pan (don't crowd the pan).
Brown meat well on all sides; remove from the pan and set aside.
Add the onion and the veggies you are using. Saute about 3 minutes.
Add the stock to the pan and add the reserved meat. Bring to boil, cover and reduce heat to low and cook for 30 minutes.
Whisk in the thickening mixture and whisk until it's well incorporated and juice begins to thicken.
Preheat oven to 400 degrees F.
Place the meat mixture in a 2-quart casserole or a deep-dish pie pan.
Cut a slit in the pastry to allow steam to escape and lay the sheet of pastry on top of the meat mixture (you don't have to crimp or seal--laying on top is sufficient). Brush pastry top with milk.
Bake for 30-35 minutes or until crust top is puffy and deep golden brown.