Start by making the pastry. Place the flour and salt in a bowl and add in the cubed butter. Rub the butter and flour between your fingers until you have what resembles fine bread crumbs.
Add in the eggs, vinegar and milk and stir with a knife until the dough starts to come together.
Bring the dough together with your hands and form into a disc. Flatten it and wrap in cling film and place in the fridge for 30 minutes.
Now to make the filling. Melt the butter in a wide bottom pan and add in the onion. Cover and cook for around 15 minutes until softened.
Add in the diced potato and continue to cook for a further ten minutes.
Pour into a bowl and allow to cool.
Preheat the oven to 180oc.
Once the pastry has rested and the filling is cooled, roll out the pastry on a floured surface to around 5mm thickness.
I used a glass mixing bowl to cut around using a knife to create my circles of pastry.
Place the pastry circles onto a baking tray and brush the edges with the beaten egg.
Add the cream and cheese to the cooled onion and potato mixture and season well with salt and pepper.
Spoon some of the mixture onto one half of the pastry, then fold the other half over.
I used a fork to press the edges together.
Brush the pasty all over with the beaten egg then make couple of small slices on the top to enable steam to escape during cooking.
Place in the oven for 25-30 minutes until golden.
Serve with a green salad.