Whisk together the flour, baking soda, baking powder, and salt. Set aside.

In a large mixing bowl, beat the softened butter, tahini, granulated sugar, and brown sugar together until light and fluffy—about 2-3 minutes. Add the egg and vanilla extract, and mix until well combined.

Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Stir in the chocolate chips or chunks until evenly distributed.

Cover and chill the dough for an hour or up to overnight.

Scoop the dough into balls (about 2 tablespoons each) and place them on the prepared baking sheets, leaving space between each cookie.

Bake one pan at a time for 12-14 minutes, until the edges are golden but the centers still look a bit soft. They will continue to firm up as they cool. (Go with the longer baking time if you want crisper cookies.)

Let the cookies cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely. Sprinkle with flaky sea salt if desired.