Cheese, Onion and Potato Pie

Instructions:
step 1 Boil potatoes in salted water until tender, about 15–20 minutes. Drain and mash with a pinch of salt and pepper.
step 2 In a pan, heat butter or oil and cook onions until soft and golden, about 8–10 minutes.
step 3 Mix the mashed potatoes, cooked onions, grated cheese, herbs, salt, and pepper in a bowl. Let the mixture cool.
step 4 To make the pastry, rub cold butter into flour and salt until crumbly. Add cold water slowly until a dough forms.
step 5 Roll out two-thirds of the pastry and line a greased square or rectangular baking tin.
step 6 Fill the pastry base with the potato mixture and smooth the top.
step 7 Roll out remaining pastry and cut into strips for a lattice topping, or cover fully and cut slits for steam.
step 8 Arrange tomato slices on top and brush with egg wash if using.
step 9 Bake in a preheated oven at 200°C (180°C fan) for 35–40 minutes until the crust is golden and the filling is heated through.
step 10 Let it cool slightly before slicing into squares and serving.

Storage and Reheating Tips:
Store pie slices in the fridge in an airtight container for up to 3 days. Reheat in the oven at 180°C until warm and the pastry is crisp. Can also be enjoyed cold or at room temperature.