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 325°F. Line two baking sheets with parchment paper.
Divide the dough into 1 1/2 tablespoon-sized balls using a spring-loaded scoop. Bake for 12-15 minutes or until cookies are firm and slightly golden brown at the edges. Cool on the baking sheet for 5 minutes, then transfer to wire racks to cool completely.