Preheat oven to 350°F. Line a baking sheet with parchment paper or greased foil. Set aside for later.
In a medium bowl, whisk together all the dry ingredients: oat flour, cocoa powder, baking soda, baking powder and salt.
In a large bowl, whisk together all the wet ingredients: coconut oil, coconut sugar, maple syrup, flax eggs and vanilla. Whisk until thoroughly combined.
Add the dry ingredients to the wet ingredients. Whisk until you get a sticky, soft dough-like mixture. Fold in chocolate chips and walnuts.
Cover the bowl of cookie dough. Let sit for 10-15 minutes at room temperature—this allows the dry mixture to absorb the wet mixture and become more cohesive.*
Using a cookie scoop, scoop 2 tablespoons of cookie dough onto the prepared baking sheet. Using a fork, flatten cookies into a round disc of desired thickness—they won’t spread much during baking. Press chocolate chips and walnuts into the tops of the cookies.
Bake for 8-14 minutes. Mine took 10 minutes. Using a flat, heatproof spatula, carefully lift cookies off the baking sheet and transfer to a cooling rack. Allow to cool completely.
In a microwave safe bowl, add ¼ cup chocolate chips and ¼ teaspoon melted coconut oil. Heat in 20-second increments until softened and melted. Stir until smooth. Spoon melted chocolate into a small zip bag and trim a tiny corner off. Pipe chocolate in a zigzag pattern across the top of each cookie.