Make the pastry. Put the 50ml oil and 100g flour in a bowl and add about 50ml water until you have a soft dough. How to make pastry using oil hints. Leave to rest while you make the filling
Pie Filling
Sauté the onion in the 5ml of oil until soft.
Add the mushrooms and cook until they have released their water.
Mix the 15g flour with 100ml water and add to the pan. Stir around until thickened.
Season, but be light handed with the salt as you will be adding the corned beef which is salty. Stir in the chopped corned beef . Leave to cool a little.
Assemble the pie
Roll out just two thirds of the pastry and use to line a flan dish etc big enough for two portions.
Pile in the filling mixture
Roll out the remaining third of the pastry and place over the filling
Bake the pie at 180C/160 fan/Gas 4 for about 30 minutes until golden
Meanwhile cook and mash the potatoes and cook the peas.