How do they get the holes in a crumpet?

Question

How do they get the holes in a crumpet?

Answer 1

Its part of the baking process, air or gas bubbles produced by the ingredients most likely the baking soda.....

Answer 2

They are cooked to brown on one side only, resulting in a smooth darker side where it has been heated by the griddle, then lightly cooked on the other side which has holes where bubbles have risen to the surface during cooking