Line a baking tray with grease-proof paper and place to one side for later
Mix together the flax meal with the water in a small bowl and set aside for at least 5 minutes to thicken into 2 flax 'eggs'
In a mixing bowl, beat together the peanut butter, butter and sugars until a thick but relatively smooth creamy mixture forms (there will be peanut chunks)
Add in the vanilla extract and flax egg to the bowl and mix in
Add in the flour, baking soda and baking powder to the bowl and continue to beat the mixture together (do not panic if it becomes slightly crumbly - the more you mix, the more it will bind together)
If the mixture is too stiff/dry, add 1-2 tbsp of dairy-free milk to thin it slightly (different brands of flour and peanut butter may cause varying degrees of dryness in the batter)
Add in your choice of chocolate chips and then mix thoroughly until evenly distributed throughout the dough
Place the bowl of cookie dough into the fridge for at least 4 hours to make sure the fats are cooled (this prevents the cookies from spreading too much)
Before removing the dough from the fridge, pre-heat the oven to 200°C (conventional) or 180°C (fan)
Using a large ice cream scoop (or other similar utensil), take generous portions of cold cookie dough and place them onto your lined baking tray in balls (feel free to flatten them slightly if preferred as they do tend to keep quite thick when baking)
Bake the cookies in the oven for 12-14 minutes (until slightly golden in colour)
Once baked, leave them to cool on the tray for at least 30 minutes before moving (as they will be delicate as only half-baked at this point - they continue to bake on the tray)
Once cooled, you can move the cookies onto a wire cooling rack to make sure they are completely cooled and ready to eat
Break the cookies in two to reveal the gooey centre and enjoy!