To make the dough sift together the dry ingredients. Cut butter into the flour with a knife and then rub it in with your fingers until the mixture resembles dried breadcrumbs.
Beat the milk and egg together. Make a well in the flour mixture and add the liquid gradually. Mix quickly to a soft dough. Turn out onto a floured board and knead lightly until smooth. Roll out into a square approximately 10mm thick. To make the filling mix all ingredients together and spread over the dough keeping 25mm clear along the edges. Roll up dough like a Swiss roll and seal the edges with beaten egg and water. Wrap lightly in greaseproof paper and refrigerate for about 30 minutes. Carefully cut the dough into 25mm slices and arrange them - cut side down - on the bottom of a greased No.3 cast iron pot. Begin in the centre and arrange the remaining slices in a circle. Leave the sides of the pot clear to allow the dough to rise. Grease the inside of the lid with cooking oil or butter and cover the pot. Put the pot over a small fire - put a few small hot coals on the lid and bake for 20 - 30 minutes until the bread is golden brown and cooked. Turn out - cool slightly - and then serve with crisp vegetable sticks and lettuce leaves.