Preheat oven to 350°F and line a cookie sheet with a non-stick silicone mat or parchment paper.
Make a vegan 'egg' by mixing the ground chia seeds and water in a small bowl. Let it gel up while you start the cookie dough.
In a medium mixing bowl, cream together the coconut oil and coconut sugar until homogeneous. Add the vanilla extract, salt, and vegan 'egg' and mix until even.
Add the baking soda, oat flour, and oats and mix until combined. Fold in the walnuts and chocolate chunks.
Portion out golf ball-sized pieces of cookie dough and flatten until about ¾" thick. These cookies don't spread much in the oven so shape them as desired. Arrange cookie dough on prepared cookie sheet.
Bake in the preheated oven for 12-15 minutes, or until edges are lightly browned, just before the centre is set. Cool on the pan for 5 minutes and then enjoy!
Notes
*Those that are not vegan may choose to use a normal egg
Recipe by Radiant Rachels at https://radiantrachels.com/vegan-walnut-chocolate-chunk-oatmeal-cookies/