Pre heat the oven to 185°C.
Place a heavy based saucepan on a medium heat. Add the butter and cook until it begins to colour then remove from the heat and add a dash of hot water to stop the cooking process. Make sure you stand back from the pan as it is likely to spit.
Put the oatmeal in a large bowl, add bicarbonate of soda, salt, butter and hot water, and stir well with a wooden spoon. Finally use your hands to bring the soft paste together.
Sprinkle your work surface with plain flour and roll out the dough, roughly 1cm thick. Use a cutter to mark out the rounds and leave to cool in the fridge for 30 minutes or so to stop shrinkage.
Place on a cold baking tray and bake in the oven for about 20-25 minutes. Remove from oven and allow to cool a little then place on a wire rack to cool completely.