In a large bowl measure out and mix the different flours and salt. In a jug, add the milk, water, yeast and sugar. Leave for ten minutes or so until frothy. Then combine the wet ingredients with the dry ingredients. Cover and leave overnight in a cool place.
The next day, retrieve the batter and melt a little butter, not too much, on on the pan on a medium heat.
Add a ladle of batter to the pan and tip the sides until you have a thin 10 inch/20cm circle. Let it bubble and pop in a crumpet like fashion. Do not hurry this process, and only turn the oatcake towards the end when the top is set. Then add the melted cheese.
Don't worry about the first one, like pancakes, they always go wrong.
Oatcakes can be served with sweet fillings, such as blackberries and cream.
Oatcakes can be made in advance and frozen.