This recipe was inspired by Anzac biscuits, a popular cookie in Australia and New Zealand that is packed with coconut and oats. Oats enhance the nutty flavor and crisp-chewy texture of coconut but to make sure the coconut is the star in these cookies, I added ground and flaked coconut to the batter along with a bit of coconut extract and garnished with a sprinkling of toasted coconut.
Position racks in the upper and lower thirds of the oven and preheat to 350˚ F. Line 2 baking sheets with parchment paper. Combine 1/2 cup coconut flakes with the granulated sugar in a blender and process until the sugar is finely ground and the coconut is in very small pieces.
Put the butter in a large microwave-safe bowl and microwave until melted; let cool slightly. Stir in the coconut-sugar mixture, brown sugar, salt, baking soda and coconut extract, then stir in the oats. Add the flour and 1/2 cup coconut flakes and stir to combine.
Scoop heaping tablespoonfuls of dough and gently shape into balls. Arrange about 2 inches apart on the baking sheets. Bake, switching the pans halfway through, until the cookies are set around the edges and the centers are puffy, 16 to 18 minutes. Let cool 3 to 5 minutes on the pans, then remove to a rack to cool completely. (For crunchy cookies, gently flatten the dough balls and bake until browned all over, 18 to 20 minutes.)
Put the remaining 1/2 cup coconut flakes in a medium skillet and cook over medium heat, stirring, until toasted, 5 to 7 minutes; let cool. Put the chocolate in a microwave-safe bowl and microwave in 30-second intervals, stirring, until melted and smooth. Transfer to a small resealable plastic bag and snip a corner. Drizzle the chocolate over the cookies, then sprinkle with the toasted coconut. Let the chocolate set, 10 to 15 minutes.