Preheat oven to 350°F. Line a baking sheet (18 x 13 inches) with parchment paper.
Place flour, coconut, baking soda, baking powder and kosher salt in a medium-sized bowl and whisk for 30 seconds to thoroughly combine.
Place butter, brown sugar and granulated sugar in the bowl of a stand mixer. Mix on low speed with the paddle attachment for about 30 seconds. Increase speed to medium and beat for about 2 minutes, until the butter and sugar combination looks creamy and is lighter in color.
Add egg, egg yolk and vanilla extract and mix on medium until thoroughly incorporated. Scrape down the sides and bottom of the bowl and make sure to scrape all the batter off the paddle attachment.
Add flour mixture and mix on low speed until thoroughly incorporated. If there is any flour left on the sides of the mixing bowl, scrape with a silicone spatula and mix in by hand.
At this point you can bake the cookies right away, or store in the refrigerator for 1 hour to up 3 days.
Place ¾ cup coconut in a small bowl.
For small cookies, use a size #40 cookie scoop (about 4 teaspoons or 25 grams) and scoop 10 cookies about 2 inches apart on the baking sheet. Arrange the cookies in rows like this: 3-2-3-2. Then take each ball of dough and roll in the shredded coconut.
For large cookies, use a ¾ cup scoop and place 6 cookies at a time on the baking sheet. Roll in shredded coconut.
Bake 10–12 minutes, or until the edges are golden brown and the coconut on the edges of the cookies have turned golden brown. Let cookies cool for 2 minutes, then remove to a wire rack to finish cooling.
Wait for baking sheet to cool before adding the next batch of cookies.
Cookies can be stored for up to 1 week in an airtight container.