If using porridge oats, whizz in the food processor for a few seconds.
Mix all of the dry ingredients together. Rub in the spread or mix in the food processor - the resulting mixture should be fairly dry and will look something like the Sahara desert - don't worry, it will stick together as it cooks!
Tip the mixture into a well greased baking tray (25x30cm) and press down firmly with the back of a spoon.
Bake for 25 to 30 minutes or until golden brown. Remove from the oven and mark into pieces with a sharp knife. Allow to cool fully in the tray before removing and breaking up.