Spray an 8x8” brownie pan with cooking spray and line with parchment paper both ways for easy removal later.
In a large bowl, stir together the oat flour and 1 cup of the oats. Add the melted coconut oil, maple syrup, vanilla extract, and salt. Mix until thoroughly combined
Fold in the walnuts pieces. Reserve 1⅓ cups of the mixture into a small bowl. Dump the remaining base mixture into the prepared pan and flatten it out.
In a medium-sized microwave-safe bowl, add the chocolate chips. Microwave at 30-seconds intervals, stirring between each one, until completely melted. Whisk in the coconut milk. Mixture should thicken and turn into a smooth ganache. Spread the mixture over the base (I used an offset spatula).
To the bowl with the reserved base mixture, stir in the remaining 2 tbs of oats. Sprinkle this over the chocolate layer and press it into the surface. Feel free to press in some more walnut pieces if you're craving some additional crunch! Cover and refrigerate overnight.
Bring the bars out of the fridge 20 minutes before slicing to soften. Slice, serve, and enjoy!