1 small onion, chopped
leftover gravy
175g/6oz plain flour
pinch of salt
40²µ/1Β½΄Η³ϊ butter
1 tbsp oil or butter
1 free-range egg, beaten with a drop of milk
40²µ/1Β½΄Η³ϊ lard
1 thick slice bread
125²µ/4Β½΄Η³ϊ roast beef, or other cooked meat