Heat oven to 350°F. Line two baking sheets with parchment.
Toast coconut on a sheet, 5–7 minutes, stirring once, until golden. Cool completely.
Cream softened butter, brown sugar, and granulated sugar until light and fluffy, 2–3 minutes.
Beat in the beaten eggs and vanilla until smooth and glossy.
Whisk flour, baking soda, baking powder, cornstarch, and salt in a bowl.
Mix dry ingredients into the butter mixture on low just until combined; do not overmix.
Fold in toasted coconut and chocolate chips until evenly distributed.
Chill dough 20 minutes to help control spread.
Scoop 1½-tablespoon portions onto sheets, spacing 2 inches apart.
Bake 9–12 minutes until edges set and centers are slightly soft. Cool 5 minutes, then move to a rack.