Makes about 22 cookies
In a bowl set over pan of barely simmering water, melt 5 ounces coarsely chopped chocolate until smooth. Cool 15 minutes.
In large bowl, whisk sugar with cocoa until combined. Whisk in whites, salt, vanilla, and coconut extract. Whisk in chocolate mixture until smooth. Fold in coconut and the remaining 2 ounces finely chopped chocolate. Chill until firm enough to scoop, about 30 minutes or overnight.
Adjust the oven rack to upper-middle position and lower-middle position and preheat oven to 350°F. Line two baking sheets with parchment paper or preferably a non-stick baking liner. If using parchment, lightly grease.
Using a scoop or tablespoon, portion batter by two tablespoon mounds each, spacing evenly onto pans (about 12 cookies per pan). Form into mounds.
Bake until set on the edges and center is still slightly soft, about 15 to 16 minutes. Let cookies cool on pan 10 minutes, then transfer to wire rack to cool.
5 ounces bittersweet chocolate, chopped coarsely
2/3 cup granulated sugar
1/4 cup (3/4 ounce) unsweetened cocoa powder
3 large egg whites
1/4 teaspoon kosher salt
1 teaspoon pure vanilla extract
1/4 teaspoon pure coconut extract
2 1/2 cups sweetened flaked coconut
2 ounces bittersweet finely chocolate, chopped into ¼-inch pieces