In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, brown sugar, and granulated sugar together on medium speed until light and fluffy (2-3 minutes). Then add the egg and vanilla and continue beating until creamy.
In a separate bowl, mix together the flour, cornstarch, baking soda, salt, and pinch of cinnamon. Then add this mixture to the other ingredients, mixing on low speed until the flour is just combined.
Fold in the chocolate chips and shredded coconut.
Cover and transfer the dough to the fridge to chill for at least 30 minutes, or overnight.
When you're ready to bake, preheat the oven to 350°F and line two cookie sheets with parchment paper. Scoop 1.5 tablespoon balls of dough onto the cookie sheets, making sure to space them 2" apart. Bake for 12-14 minutes, or until the edges are golden brown.
Let the cookies rest for 5 minutes on the baking sheets before transferring to wire racks to cool completely. Enjoy!