Add the stock and thyme and boil until the liquid is reduced by about a third.
In a smaller pan lightly cook the cubed pheasant with 1 Tbsp. of butter and 1/4 tsp. of dried thyme (no longer than 5 minutes as pheasant gets tough when overcooked).
Add carrots, potato (peeled and diced), celery and pheasant to the boiling stock mix and reduce to a simmer. Cook until the vegetables are tender and the pheasant is completely cooked through.
Layer one of the pre-made crusts into a deep-dish pie pan. Pour mixture onto crust and cover with second crust. Slit holes in crust for ventilation.
Bake pie for about 35 to 45 minutes, or until the crust is golden brown and the filling is starting to bubble over.