In a small bowl, mix the flax with 3 tbsp water. Allow to sit for 5 minutes.
Mix all ingredients well in a large bowl. Roll approx. 1 tbsp of dough into a ball to make 1 cookie and place on pan. Press down gently with a fork to flatten. Top with optional toppings.
Bake for 10 minutes, until slightly browned on the edges. Let cool for 5 minutes on the pan. Cookies will be very soft when removed from the oven, but will slightly harden as they cool.
Notes
Peanut butter is low FODMAP at 2 tbsp. The maximum FODMAP serving size per sitting for this recipe is 3 cookies.
A large egg can be used in place of the ground flax. Do not mix the egg with water.
The vanilla and salt add flavour to the cookies, but are not essential for the recipe.
In Canada, peanut m&ms do not contain high fructose corn syrup, but do contain milk chocolate and lactose. Limit to 2 pieces in one serving to keep the lactose low. Omit peanut m&ms if very lactose intolerant or vegan.
If you make this with salted peanut butter, you may omit the added salt.
This recipe can also be made with other nut/seed butters (like sunflower seed butter) in place of peanut butter (good for peanut allergies or for putting in school lunches)