INSTRUCTIONS

1. Preheat oven to 350°F. Line a baking sheet with parchment.
2. Chop chocolate into 1-in pieces. Reserve 28 pieces of dark chocolate for garnish.
3. Stir flours with cocoa powder, baking soda, salt and instant espresso, if using, in a medium bowl. Set aside.
4. Combine butter, tahini and sugars in a large bowl. Beat, using an electric mixer on medium speed, until light in colour and tripled in size, about 5 minutes. Switch mixer to low. Beat in the vanilla. Add the eggs, beating between each addition, until smooth.
5. Add dry ingredients and stir, using a wooden spoon, until stir combined. Stir in chocolate, keeping reserved garnish aside.
6. Roll dough into 1 1/4-in balls. Arrange, 2-in apart, on prepared baking sheet. Gently flatten each ball into a disc. Press a piece of the reserved dark chocolate into the top of each cookie.
7. Bake, in centre of oven, for 4 minutes. Remove baking sheet from oven and evenly bang on stovetop 8 to 10 times to deflate cookies. Return to oven. Bake for 3 minutes then repeat the banging process.
8. Let cool on baking sheet for 5 minutes; transfer to a wire rack to cool completely. If desired, sprinkle with sea salt. Repeat until all cookies are baked.