Preheat the oven to 175 C. Line a baking tray with a silicone mat or grease the tray. The cookies tend to stick so the mat is more convenient.<br></br>

In a small bowl, mix the oats, cinnamon and baking soda.<br></br>

In a larger bowl, mix the peanut butter, sugar, egg and vanilla till well combined.<br></br>

Fold in the oats. You will now have a thick, sticky cookie dough. Fold in the chocolate chunks if using.<br></br>

Use a tablespoon measure or a cookie/ice cream scoop to make equal sized dollops of the dough. Place an inch apart on the tray. Use a small spoon to help shape them into rounds, or leave them as is.<br></br>

Bake for 10 minutes, then 3 to 4 minutes more if you would like more colour or crispiness. However, the cookies remain soft in the middle, and the edges begin to soften after a couple of hours. Allow to cool completely, then store in the fridge if not eating immediately. Happy baking!