Peel the potatoes and boil them in salted water until tender. Drain well.
Heat 1 tbsp of the olive oil in a pan and cook the onion until soft and lightly golden.
Mash the potatoes roughly, leaving some texture.
Add the onion, milk, eggs, cheese, feta, oregano and black pepper. Mix well.
Add the olive oil into the mixture and mix well (save 1 tbsp to top the pie).
Transfer to a lightly oiled 22 cm tin and smooth the top and add the remaining olive oil and spread it to the top with a brush.
Bake to a preheated oven at 180°C fan for 60- 65 minutes, or until golden and set.
Allow to rest before slicing and serving.
