Preheat your oven to 350 degrees Fahrenheit and line a 9x9 baking sheet with parchment paper or grease with coconut oil.

Prepare your flax eggs by adding the ground flax and water in a small bowl. Stir to combine and set aside to thicken.

In a large bowl, add the oat flour, cocoa powder, almond flour, baking powder, and baking soda. Stir to combine.

Add the dates and water to a small blender. Blend on high until a smooth date paste forms. Add the date paste, prepared flax egg, apple cider vinegar, melted coconut oil, and almond butter to the bowl. Stir until combined.

Add the mixture to your prepared pan and smooth evenly. Top with walnuts or chocolate chunks if desired.

Bake in the preheated oven for 28-20 minutes. Let cool before cutting into 12 slices. Store in the fridge or freezer.