Combine the oats, flour, sugar and salt in a large bowl and rub in the butter with your fingertips until it resembles coarse breadcrumbs.
Add the beaten egg and combine well with a wooden spoon to form a dough.
Divide the dough in half. Wrap each half in cling film and chill for 20 minutes.
Dust your work surface with some porridge oats and roll out the dough to a 1/4 inch thickness, sprinkling more porridge oats over the top of the oatcakes to help the dough roll out. Cut out your oatcakes with a 5 cm round fluted cutter.
Carefully transfer each oatcake to an ungreased baking sheet, placing about an inch apart as they don't spread much.
Bake for 15 minutes and transfer to a wire rack to cool completely.
Store in an airtight container until needed.
Mum of three, daydream adventurer, OU Life Sciences graduate, occasional crafter, ex-pat Canadian & quite possibly Britain's most northerly food blogger.