Sauteé mushrooms and onions in butter until tender but not browned.
Combine flour and spices. Blend into flour mixture slowly so it doesn’t get all lumpy.
Slowly stir in gravy (again: lumps). Add everything else and heat on low.
Prepare biscuits for base: use any recipe but add 1 tsp poultry seasoning for every cup of flour. Mix the poultry seasoning with all the dry ingredients.