Prepare the biscuit dough by adding flour, sugar, salt, baking powder, and baking soda to a large bowl. Mix well.
Dice or grate the cold butter into small pieces and add to the flour mixture. Cut the butter into the flour until evenly distributed.
Add sourdough starter and buttermilk, stirring until just combined. Cover the dough and keep it in the refrigerator.
Start the filling by adding butter, garlic, onion, potatoes, and carrots to a large cast iron skillet on medium-low heat. Sauté for 10 minutes.
Sprinkle the flour over the sautéed vegetables, then stir and cook for a few minutes.
Pour in the bone broth and add parsley, salt, pepper, garlic powder, and onion powder. Mix well, cover, and cook for 10 minutes.
Stir in peas, pre-cooked chicken, and heavy cream, then transfer the filling to a greased 9x13 baking dish.
Preheat oven to 400 degrees Fahrenheit. Roll biscuit dough onto a lightly floured surface and cut out biscuits.
Place biscuits on top of the pot pie filling. Bake for 10-15 minutes or until the biscuits are golden and the filling is bubbling.
