Preheat the oven to 350 degrees Fahrenheit.
In a small bowl, whisk together the ground flax and water. Set aside for 10 minutes to thicken.
Meanwhile, whisk together all wet ingredients until smooth, add in the flax mixture once thickened.
Add in all dry ingredients, aside from the chocolate chips. The batter will be thick.
Fold in the chocolate chips.
Add to an 8x8 baking pan lined with parchment paper. Spread evenly with a rubber spatula. Top with additional chocolate chips if desired.
Bake for 22-30 minutes or until a toothpick comes out clean. I usually do 25 minutes, but all ovens are different. Bake for a shorter time if you prefer a gooier center, or longer if you like them more well done.
Remove from the oven and let cool for 10 minutes in the pan. Carefully remove from the pan by lifting up the parchment paper (slicing around the edges first as needed). Let cool on a cooling rack, then slice into 16 squares.