Preheat oven to 350° F. Line two cookie sheets with parchment paper and set aside.
In a large bowl, add the flour, baking soda, baking powder and salt. Whisk together and set aside.
Chop the chocolate in bite-sized pieces — 6 oz of chocolate will be added to the cookie dough and 2 oz will be added to the top of each dough ball before baking.
In a mixing bowl, add the butter. On high speed, cream the butter until fluffy.
With the mixer on medium speed, add in the white and brown sugars. Bring the mixer back to high speed and mix until light and fluffy and completely blended.
Next, bring the mixer down to low speed and add in the egg and vanilla extract. Place the mixer back to medium-high speed and mix until completely combined. Scrape down the sides of the bowl as needed.
Add the tahini and mix well until combined.
Bring the mixer to low speed and slowly add in the flour mixture one large spoonful at a time. Once all the flour mixture is added, turn the mixer up to medium-high speed and mix until completely combined and the cookie dough is formed.
Fold in 6 oz of the chopped chocolate.
Using a cookie scoop, scoop onto the prepared cookie sheet. Spacing should be 2 inches apart.
Place a chocolate chunk on top of each dough ball. Gently press into dough so it adheres.
Bake for 9-11 minutes. Edges and tops should be golden brown.
As you pull the cookie sheet out of the oven, tap it on the counter. This will deflate the puffiness of the cookie. You will be left with a beautiful crinkled, golden brown cookie.
Let cool for 10 minutes and then sprinkle with sea salt.
Can be served warm or at room temperature.