Preheat oven to 180c fan, 200c, 400f (gas mark 6).
Peel and grate potatoes, and squeeze of excess liquid. Add to a bowl and season with a pinch of salt and black pepper.
Spread out on a baking tray lined with parchment and spray over the top with low-calorie cooking spray.
Place in the oven and bake for 10mins, just to dry out slightly.
In the meantime, spray a frying pan over a medium high heat with low-calorie cooking spray. Add the turkey mince or Quorn mince, salt, sage and paprika and fry till lightly browned, breaking up slightly with the back of spoon (I like to leave it in bigger pieces, so don’t break it up too much).
Once the mince is lightly browned, add it to a casserole dish and allow to cool.
Whisk the egg whites or egg substitute and pour over the top of the sausage.
Add the part cooked grated potato to the top and spread out evenly.
Place back in the oven and bake for 30 mins until the potato on top is golden and light crisp.
Add the grated cheese and place under the grill for 5 mins till melted.
Optional: Sprinkle over the top with sliced spring onions (or you can use chives or fresh Italian parsley).