Preheat oven to 350 degrees. Prepare flax egg by combining 2 TBSP ground flaxseed and 5 TBSP warm water. Set aside the mixture.
In a medium bowl, cream together peanut butter, melted and cooled coconut oil, vanilla extract, and coconut sugar.
In a separate bowl, whisk together almond flour and baking soda.
Add almond flour to peanut butter mixture and fold to combine. Add almond milk to help mix. Finally, add in the prepared flax eggs and stir to thoroughly combine.
Chop up your bar of chocolate and add to batter, reserving some chunks to press on top of bars. Alternatively, you can use chocolate chips and fold these into your batter.
Transfer batter to a lightly greased pan (with coconut oil). Gently press batter down so that it is evenly distributed and packed throughout the pan. Press more chocolate on top of bars.
Bake for 20 minutes or until golden brown around the edges. Let cool for 15 minutes before slicing and serving.