For the pastry:

1. Preheat the oven to 400℉ and grease a medium-large casserole dish.
2. Place the flour, baking powder and salt in a bowl and stir to combine.
3. Use a pastry blender to mix the shortening and butter into the flour mixture until a fine crumb resembling small peas develops.
4. Stir in the ice cold water and bring the dough together in a ball.
5. Chill in the refrigerator while you prepare the other ingredients.

For the base:

1. Peel the sweet potatoes, cut into even pieces and place in a saucepan with water to cover.
2. Bring to a boil then lower to a brisk simmer and cook until tender – about 15 minutes.
3. Heat a saucepan over medium heat, melt the butter and add the onions cooking until just translucent. Add the savory, summer savory and milk and reduce the heat to minimum to keep this mixture just warm. When the potatoes are cooked, add the milk and onion mixture and mash until soft. Set aside.
4. Empty the salmon, including the juices and bones, into a large bowl and use the tines of a fork to mash it – especially the bones – to a fine texture. Squeeze any water from the thawed spinach and add just the spinach to the salmon – mixing thoroughly. Season with the salt and pepper.
5. Spread half of the sweet potato mixture in the prepared casserole dish, add all the salmon and spinach mixture in another layer and then top with the remaining sweet potato mixture.
6. Remove the pastry from the refrigerator, roll it out and then add it to the top of the casserole.
7. Brush the top with milk and make slits or a fish design in the the crust to allow steam to escape while cooking.
8. Bake for 30 minutes or until the crust is golden brown.
9. Enjoy with your favourite pickles or a nice salad.