Not a grandchild joke Gil. Perhaps you need to be Scottish to fully get the meaning behind it.
Here we have fish and chip shops (we had one) the fish is cooked in batter. now they are served in cardboard boxes simlilar to pizzas but before they were just wrapped up in paper and then people would eat the fish supper when walking home. A favourite with this was a tub of 'mushy peas' poured on top of the fish supper. (dried peas that had been soaked in water overnight then overcooked until they almost looked like a very thick pea sauce) My mouth is watering at the thought of that. You also got salt vinegar and brown 'chip shop' sauce on the supper too. Yum Yum!! I can almost smell them cooking