Preheat the oven to 200C/400F/gas 6.
Dust the baking sheet with flour.
Place the flours, porridge oats, bicarbonate of soda and salt in the mixing bowl and stir thoroughly.
Rub in the butter until you have a breadcrumb consistency. You can do this in a food processor if you want to save time.
Pour in the buttermilk and mix it in quickly with the palette knife.
Bring the dough together very lightly with your fingertips.
Transfer to a lightly floured work surface.
Shape it into a flat, round loaf measuring 20cm diameter.
Put the loaf on the baking sheet and score a deep cross in the top. (Traditionally, this lets the fairies out, but it also helps the bread to cook through.)
Place in the oven and bake for 30-35 minutes until the bottom of the loaf sounds hollow when tapped. If it isn’t ready after this time, turn it upside down on the baking sheet and bake for a few minutes more.
Transfer to the cooling rack, cover with a clean tea cloth (this keeps the crust nice and soft) and leave to cool.
To serve, break into quarters, then break or cut each quarter in half to make 8 wedges or slices – or simply slice across. Eat very fresh with lashings of butter.
