My Grandad makes the most amazing C&O pie. All he does is lightly fry the onion in some butter until translucent. Cut cheese into 1 inch size cubes. Add to pie dish and season (lightly on the salt as you will get the salty taste from the cheese). Cover, brush with egg and bake at 190 until lovely and golden. Unable to give you quantities I'm afraid, as Grandad used to make this in HUGE quantities... Plus he never measured anything. But if I remember rightly, it always used to look about equal quantities of cheese and onion. In my defence, I misread your question, and thought you specified don't answer if it DID contain potato. But to quote your remark to 'Answerer 1': - Since when has cheese and vegetable been cheese and onion answerer number 1 So in the same resepect... Since when has CHEESE AND ONION PIE been Cheese, Onion and Potato Pie??? Need to sort it out mate!