Preheat the oven to 180C/350F. Line a large baking tray or cookie sheet with parchment paper and set aside.
In a high-speed blender or food processor, add your oats, baking powder, baking soda, salt, and sugar and blend until combined and the oats are coarse.
In a large mixing bowl, add your blender ingredients. Add your coconut oil (or butter), vanilla extract, and milk and mix until combined. Fold through your mix-ins of choice (depending on which cookie option you choose), reserving a few to top the cookies with.
Form 12 small balls of dough onto the lined tray or cookie sheet. Press on each ball into a cookie shape and top with extra mix-in ingredients. Bake for 10 minutes, before removing from the oven and letting cool on the pan completely.
Notes
TO STORE. Flourless cookies should be kept in an airtight container at room temperature for up to 5 days or in the fridge for up to 2 weeks. TO FREEZE. Store cooled cookies in a freezer-safe container and freeze for up to 6 months.