Arrange racks in the top and bottom thirds of the oven; preheat to 350°F. In a large bowl, mix the coconut and cocoa powder. In another bowl, using an electric mixer, beat the egg whites and ½ teaspoon kosher salt until soft peaks form, 1 to 2 minutes. With the mixer running, gradually add the granulated sugar. Continue to beat until the meringue is very stiff, 2 to 3 minutes. Beat in 1 tablespoon vanilla. Gently fold the coconut into the meringue.

Using a tablespoon measure, scoop the coconut mixture into balls and divide them between 2 parchment paper-lined baking sheets. Bake, rotating and reversing the sheets halfway through, until the macaroons are slightly crisp on the outside but still soft inside, about 18 minutes. Let cool for 5 minutes. Transfer to wire racks to cool completely.

In a medium bowl, whisk the confectioners’ sugar, tahini, a pinch each of cinnamon and kosher salt, the remaining 1 teaspoon vanilla, and 2 tablespoons water until smooth. Spoon some glaze over each macaroon. Top with sprinkles.