Preheat oven to 450ยบ F.
Heat the olive oil in a large skillet over medium high heat. Add the pork and cook for 6 - 8 minutes, until browned. Remove from pan and keep warm.
In the same pan, add butter, onion and celery and cook for 2 minutes, until the veggies are softened.
Stir in the flour and cook for about a minute.
Add the chicken broth and milk and whisk to combine. Reduce heat to medium and simmer, stirring often until the mixture thickens, about 5 minutes.
Stir in the peas and carrots, thyme, tarragon, salt, pepper and cooked pork. Remove from heat.
Press one pie crust into a deep dish pie pan.
Add the pork mixture and cover with the top crust. Seal the edges and cut a few vent holes.
Bake for 40 minutes, or until crust is golden brown. Cool before slicing.