Pre-heat the oven to 180 degrees C | 350 degrees F and line an 8 x 8 baking tray with baking paper.
In a small bowl, make your flax egg and set aside for 5 - 10 minutes
In a mixing bowl, add the peanut butter, coconut oil (melted but not hot), and brown sugar and stir
Fold in the flax egg and plain flour. Finally, add the milk to bring the batter together.
Carefully stir in the chocolate chips, reserving a few to scatter over the top.
Pour the batter (it will be quite thick) into the baking tray, and smooth down the top.
Bake for around 30 minutes - insert a skewer at 25 minutes first, if it comes out clean or with just a few crumbs, the blondies are done - if not, bake a little longer.
Allow the brownies to cool in the tray for 15 minutes before removing and cooling completely on a cooling rack.
These brownies are great fresh out of the oven - but they are so much better the next day when they've fully firmed up and gotten even dense and fudgier!