1. In a small bowl, whisk the flours (or flour), baking soda and salt together.
2. In the bowl of a stand mixer fitted with the paddle attachment, or by hand in a bowl with a spoon or spatula, mix the butter, both sugars, and the vanilla extract on medium speed until well combined. Mix in the tahini, then the egg, stopping the mixer and scraping down the sides to make sure everything is incorporated.
3. Stir in the flour mixture on low speed, then the figs and chocolate chips. Line a small baking sheet with parchment paper and portion cookies into 2-inch (5cm) rounds using either a spring-loaded ice cream scoop or two soup spoons, and place them on the baking sheet. For the nicest shaped cookies (after they’re baked, in step #4), roll the mounds of cookie dough gently in your hands to smooth out any rough edges. Cover and refrigerate the dough overnight.
4. To bake the cookies, preheat the oven to 350ºF (180ºC). Line a baking sheet with parchment paper or a silicone baking mat. Put the sesame seeds in a small bowl and roll each mound of chilled cookies dough in the sesame seeds to coat them, placing them about 2-inches (5cm) apart on the prepared baking sheet as you go. (The cookies don’t need to be perfectly coated with seeds; gaps are normal.) Press them down very lightly on the baking sheet, but don’t flatten them, to avoid them rolling around when you walk it over to the oven. The cookies won’t all fit on the baking sheet, so you’ll have to bake them in two batches.
5. Bake the cookies on the center rack of the oven, rotating the baking sheet midway during baking, until they are browned around the edges and very lightly browned across the top, for 15 minutes. Don’t overbake them. Remove the cookies from the oven and use a flat spatula or pancake turner to tap down the domed tops of the cookies so they’re flat. (Don’t squish them; a few gentle taps should do.) Let cool for a few minutes then transfer the cookies to a wire cooling rack. Allow the baking sheet to cool completely, then bake the remaining cookies.