Makes 18 large cookies
There`s a genius secret behind this satisfyingly fudgy cookie: It swaps tahini for butter so it`s completely vegan. Tahini is the ground sesame butter that`s ubiquitous in Middle Eastern food. Decadently smooth and nutty, this paste is at home in both savory and sweet recipes. Its contribution to this cookie is like the bass notes in a song. It adds depth of flavor and richness to the sweet and chocolaty cookie—no one will ever know it’s vegan. Before you measure out the tahini, make sure it is well stirred so the oil is evenly mixed with the thicker paste. You can use a long spoon or butter knife to get down to the bottom of the container to incorporate any dry clumps. This step makes all the difference in the final texture.
In a large bowl, whisk together the flour, arrowroot powder, kosher salt, baking soda, and baking powder.
In a stand mixer with the paddle attachment or using a handheld mixer, beat the tahini and sugars until well combined, scraping the bowl to be sure there are no clumps at the bottom. Add the water and vanilla and mix until well combined.
Add the flour mixture and mix until just combined. Add the chopped chocolate and mix until just combined, being careful not to overmix. Cover the bowl and chill the dough for at least an hour or overnight. Scoop the dough into 2 Tbsp balls. You can refrigerate the scooped dough for up to a week before baking.
To bake, heat the oven to 375°F. Arrange the cookies on parchment-lined baking sheets, leaving plenty of social distance between them (at least equal to the size of the cookies). Using slightly damp hands, flatten the dough until each cookie is about 1-inch tall. Sprinkle with sea salt and sesame seeds.
When you put the cookies in the oven, immediately turn the oven down to 350°F. Be sure to do this for each batch of cookies you bake—the higher temperature encourages the cookies to rise rapidly in the oven and lowering the temperature allows them to spread and keeps them from burning. Bake the cookies for 9 minutes, then check on them for doneness—they should be chewy, not crisp. They may need 2-3 more minutes, but be sure not to overbake.