In a bowl, whisk together the flour, cornstarch, baking soda, baking powder, and salt. Set aside.

In the bowl of a stand mixer fitted with paddle attachment, mix together the butter and both sugars on high speed until fluffy and light, scraping down sides and continuing to mix, for 3 to 4 minutes - do not skimp on this step, as it's very important for achieving correct texture. You can use an electric hand whisk if you don't own a stand mixer.

Add egg and vanilla extract, mixing until incorporated and smooth; scrape down sides as needed.

On medium-low speed, gently mix in the dry flour mixture just until incorporated, scraping down the sides as needed; do not over-mix here. Add coconut and chocolate chips and slowly mix just until combined; again, do not over-mix.

Use rubber spatula to scrape down sides of bowl and form a large dough ball. Transfer entire dough ball onto a sheet of cling wrap and wrap it up airtight; chill at least one hour in the fridge.*

When ready to bake, heat oven to 350F, with rack on lower middle position.Line baking sheets with parchment or silicone mat. Let chilled dough sit at room temp 5-10 min. while oven preheats.

Use cookie scoop to form 1 TB rounded dough balls, 2 inches apart on lined baking sheets. Bake about 8 minutes or just until edges are golden; cookies will seem slightly under-baked, but will set upon cooling.