Preheat oven to 350F and coat a 9x9 baking pan or two smaller ones with oil.
In a large bowl, combine the dry ingredients - the coconut flour, cacao powder, sea salt, and baking soda. Set aside.
In a smaller bowl, whisk together the nut butter, sugar, flax eggs, almond milk, and vanilla extract. Carefully stir the wet into the dry and mix until combined. Fold in the chocolate chips and walnut pieces.
Transfer the batter to the baking pan and bake for 20-22 minutes, or until a toothpick comes out relatively clean (relatively because you might poke a chocolate chip, not undercooked batter).
Let cool slightly before serving. Store leftovers in an airtight container in the fridge for up to two weeks.