In a large bowl combine flour, baking powder and soda. Cut in cold butter until mixture is course and crumbly.
Stir in all fresh herbs, onion powder, and garlic powder. Combine buttermilk and egg until mixture is smooth. Cover and refrigerate until ready to use.
Turkey and Vegetables Filling
Melt butter in a large saucepan. Whisk in flour until a thick paste is made. Pour in turkey stock and keep on heat to thicken for about 5-10 minutes.
In a large slow cooker combine all ingredients from saucepan, the remaining chopped turkey, vegetables, and salt. Stir until everything is uniform.
Using your hands, make small to medium sized biscuit dumplings and put on top of turkey mixture in slow cooker. Cook on low for 6-8 hours.