Sieve together the flour and salt. Dissolve the sugar in half the milk and sprinkle the yeast on top. Leave for about 10 minutes or until frothy. Add to the flour with the remaining milk and beat thoroughly for 5–10 minutes. Cover and leave to rise. Dissolve the bicarbonate of soda in the water, add to the risen mixture and leave to rise again. Lightly grease a hot griddle or thick frying pan and some 3½–4 inch pastry cutters or plain rings. Place cutters or rings on griddle or frying pan and heat. Drop spoonsful of the mixture into the cutters and allow to cook until the top is set and full of holes and the underside a pale biscuit colour. Remove the rings, turn the crumpets over and dry out for a few minutes on the other side. Allow to cool. Serve the crumpets, toasted on both sides, with butter.