Line a 8 x 8 pan with parchment paper and set aside.
In a large sauce pan, melt the peanut butter. Stir in the flax seed, vanilla, and the maple syrup and remove from the heat. The peanut butter will be runny, but as the flaxseed absorbs it will start to thicken up. Pour the peanut butter mixture into the prepared pan and smooth out the top. Place in the refrigerator to rest while you melt the chocolate.
In a double boiler, melt the chocolate, stirring constantly with a heat resistant spatula until it’s completely melted and smooth. Pour the chocolate over the peanut butter mixture and use a spoon to smooth out. Place in the refrigerator and allow the chocolate to set completely before cutting into squares.