In the bowl of a stand mixer, beat the butter, tahini, cane sugar and brown sugar on medium speed for 2 to 3 minutes, or until fluffy.
Add the egg, egg yolk and vanilla extract and beat for 1-2 minutes, until the eggs are incorporated.
In a small bowl, whisk together the flour, baking soda, and sea salt.
With the mixer on low speed, add the dry ingredients until just combined, then fold in the chocolate chips. Cover the dough and refrigerate overnight.
Preheat the oven to 325ºF. Line two baking sheets with parchment paper.
Form the cookies into balls using an ice cream scooper, or your hands. Place them evenly spaced on the baking sheets. Bake one sheet at a time, until the cookies are golden brown around the edges but still pale in the center, about 12-15 minutes.
Remove from the oven and allow to cool.