Preheat oven to 350F.
Line a 9x9 inch baking dish with parchment paper and set aside.
In a small bowl, create your flax egg by combining the ground flaxseed with warm water. Let it set for about 5 minutes.
To a large bowl, cream together the melted vegan butter, white sugar and packed brown sugar until well combined.
Add in the flax eggs, vanilla extract, espresso powder, salt and baking powder, and mix together until just combined with a hand mixer or whisk.
Using a sieve, carefully sift the cocoa powder and flour into your bowl. Begin folding in the dry ingredients with a spatula until half the flour and cocoa powder is incorporated, then add in your chocolate chips. Fold them in until JUST combined. It is important to not over-mix the dough!
Pour the batter into your lined baking dish, and bake for 40 minutes, until the top of the brownies begin to crackle.
Remove from the oven and let cool completely before cutting.