To make the pastry, weigh out the flour and butter into a mixing bowl, and add the salt. Rub the butter into the flour and salt using your finger tips until it resembles breadcrumbs. You can also do this in a food processor, or using a fork
Add the eggs and mix it together until a dough forms, do not overly knead the dough. Wrap the pastry dough in cling film and chill it in the fridge for 30 minutes
Meanwhile, make the filling. Warm up the oil and butter in a large frying pan on a low heat and add the onion and garlic. Cook for around 5 minutes until the onion has softened
Add the diced potato and fry for around 15 minutes
Add the Marmite, water and salt. Cook for 5 minutes so the potatoes can absorb plenty of the Marmite
Take off the heat and leave to cool. Once cool, mix in the grated cheddar cheese
Pre-heat your oven to 200C Fan/425F/Gas Mark 7
Roll out the pastry onto a mat or work surface dusted with flour to about 2mm thick. Use a 6" round cutter, an upside bowl or a small side plate to cut out rounds of pastry. You will need to re-roll the dough once or twice to get all 6 rounds
Spoon the filling into the centre of the pastry circle, brush the edges with the beaten egg, then fold the dough over the filling and either roll the edges over with your fingers, or crimp the edges with a fork to seal them. Then cut two small slits in the top of each pasty with a sharp knife
Move the pasties onto lined baking trays and brush them with beaten egg. Bake them for 25 minutes or until the pastry is golden all over, you can lift them up gently using a spatula, to check the pastry underneath is cooked through
Serve warm, or allow to cool and re-heat. Once fully cool, store in the fridge or they can be frozen