Preheat oven to 400'F. Lightly grease a 9" pie dish or round casserole dish.
Cook chicken breast using method of choice and set aside to cool.
Combine all ingredients for the biscuit crust and topping. Press a third of it into the bottom of the pie dish. Back for 15 minutes or until it starts to brown and no longer appears wet. Remove from oven and set aside.
While crust is baking, melt butter in the bottom of a large pan. Add onion and mushrooms and sauté until onions are translucent and mushrooms are browned.
Sprinkle coconut flour over sautéed vegetables and stir to coat. Slowly whisk in chicken broth and stir until all coconut flour is absorbed. Add rosemary and simmer 5-10 minutes or until liquid has reduced. If still too watery, mix a corn starch slurry using 1 tbs corn starch and 2 tbs cold water. Slowly add slurry to gravy mixture, incorporating completely, and let it set to thicken. (Note: You may not need all of the slurry to achieve desired thickness, so add it slowly.)
Add frozen vegetable blend and chopped chicken to the pan and toss so everything is evenly coated. Pour over pre-baked pie crust.
Use the remaining dough to form biscuits across the top of the pie dish, or flatten it out with your hands and a wooden spoon to create a top crust. Return pie to the oven and bake another 22-25 minutes or until liquid is bubbling and top crust starts to brown.