Scald the milk until hot, then leave to cool until tepid.
Mix together the fresh or dried yeast with the milk and the sugar. Leave for 5–10 minutes until frothy.
Sift the flours into a large bowl. Stir in the salt. (Add the fast-action yeast now, if using).
Make a well in the centre and pour in the frothy yeast mixture, oil and 400ml of the warm water. Beat until it makes a smooth and elastic batter.
Cover with a cloth and leave for 1½–2 hours until the mixture rises and the surface is covered with bubbles.
Dissolve the bicarbonate of soda in the remaining warm water and stir it into the batter. Cover and leave for 30 minutes.
Put a large frying pan over a medium to low heat. Lightly grease three or four 8cm metal ring moulds and put into the pan.
Pour the batter into the rings until three-quarters full and cook for about 8 minutes until the top sets and bubbles have formed on the surface.
Turn over in the moulds, pushing the crumpet down onto the pan base, and cook for 4 minutes until golden. Keep warm in a low oven. Repeat until the batter is used up.
Serve warm with butter and preserves. The crumpets can also be toasted.