1. Preheat the oven to 160°C/300°F/gas 2. Line a few baking sheets with baking parchment.
2. Cream together the peanut butter, butter and sugar until pale and creamy.
3. Mix in the beaten egg and make sure it is well mixed.
4. Sift in the flour, bicarbonate of soda and pinch of cinnamon powder. Add the oats and cranberries and stir well until it's all combined.
5. Using a tablespoon (or teaspoon for small cookies) scoop the cookie dough onto the baking sheets, lightly pressing down with the back of the spoon to flatten them a little. Leave some space between each as the dough will spread during baking.
6. Bake for 20 - 25 minutes (18 - 20 minutes for small cookies) until lightly golden brown.
7. Leave to cool on the tray for a few minutes before transferring onto a wire rack to cool completely.