Peel (if preferred) and chop the sweet potatoes into cubes and put them in a microwaveable bowl. Place in the microwave on high for 10 minute or until soft.
Put some oil into a large frying pan, or stir fry pan, and then add the sweet potatoes, rosemary, garlic and onions. Once the potatoes have started to gain some colour, add the bag of spinach to the pan.
Let the spinach wilt, stirring occasionally. While this is cooking, grease your pie dish and place a layer of thin pastry over the top. Pat the pastry down and make sure it touches the sides of the pie dish. Cut off any excess pastry around the edges.
When the spinach has wilted, pour everything from your frying pan into a mixing bowl. Crumble the feta cheese into the mix and add the two eggs. Stir until all the ingredients are combined.
Pour the mixture into your pasty pie dish, making sure it's evenly spread. Roll out another layer of thin short crust pastry and layer this over the top of your mixture.
Cut off any excess pastry and crimp the sides. Using a knife, poke a few holes in the top of the pastry to allow steam to escape. Brush the pastry with beaten egg or milk and bake in the middle shelf of the oven at 200 degrees for 45 minutes, or until golden brown on top.