In a small bowl, combine flax, espresso powder, water and vanilla. Stir and set aside.
In a large bowl using a wooden spoon or in the bowl of your stand mixer fitted with the paddle attachment, cream the butter, sugar and molasses.
Add the flax "egg" mixture to the creamed butter and sugar and mix to combine.
Add the cocoa powder and stir well.
Add flour, baking powder, baking soda and salt. Stir until just combined.
Add chocolate chips and stir to evenly distribute.
Cover and place dough in the refrigerator to rest for at least 1 hour.
After 1 hour, preheat oven to 350* F and line a sheet tray with parchment.
Scoop 6 ⅓ Cup dough mounds onto the baking sheet. Roll each mound between your palms to create balls. Then gently press the balls down onto the sheet leaving about 3 inches of space between each ball. See first picture for reference.
Sprinkle the tops of each cookie with a bit of coarse sea salt.
Bake in a 350* oven for 18-22 minutes or until the edges are set but the centers are still soft.
Allow to cool on the baking sheet for 10 minutes before transferring to a wire rack to cool completely. Repeat with the remaining cookie dough.
These cookies will keep in a n airtight container on your counter for up to 4 days or in your freezer for 1 month.