Mix flax egg in small bowl, 1 tablespoon ground flax and 3 tablespoon water. Set aside.
Add smooth tahini, brown sugar and coconut sugar to mixer bowl and beat till fully combined.
On low mixer setting, slowly add in vanilla extract, salt, baking soda, cocoa powder & flour. Mix on medium setting until batter is fully combined. May be crumbly at this point, but should hold together when squeezed in hand.
Add plant milk, 1 tablespoon at a time and allow mixer to run until batter comes together and is not crumbly.
Fold in chocolate chips
Chill cookie dough in fridge or freezer for at least 30 minutes - 1 hr.
Using clean hands, form into 2 inch balls, place onto silpat or parchment lined baking sheet and slightly press with palm to form into 1 inch thick "disk" shapes. Forms 14 cookies
Bake at 350° for 8-9 minutes. Cookies will appear soft, don't overbake! Allow to cool on baking sheet before enjoying.