Preheat oven to 350 F. Line two cookie sheets with silicone baking mats or parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment (or with an electric mixer), beat together the coconut oil and sugars until fluffy and well-combined.
Beat in eggs one at a time, scraping down the sides as needed.
Stir in vanilla extract until incorporated.
Add the flour, cornstarch, baking soda, and salt, and stir in the flour mixture until just incorporated.
Stir in chocolate chips until just combined.
Drop scoops of dough 2 inches apart onto a prepared cookie sheets using a medium cookie scoop (1 ½ tablespoons).
Bake for about 7-9 minutes. You want the edges to be just barely golden brown.
Remove from oven, and let cool for 5-10 minutes on the cookie sheet.
Transfer to wire rack to finish cooling.
Notes
Coconut oil: You'll want your coconut oil to be solid for this recipe.
If your oil is partially melted, you'll need to up the amount to 1 cup and refrigerate the dough for about 30 minutes before baking.
Brown sugar: Light brown sugar or dark brown sugar will work for this recipe.
Vanilla extract: You can reduce the vanilla to 1 teaspoon if you prefer.
Flour: I highly recommend weighing the flour. You can also sift or stir the flour to break it up, lightly spoon it into the measuring cup, and level. Avoid packing as too much flour will give you dry and heavy or crumbly cookies.
Kosher salt: If you're using table salt, you'll only need 1/2 teaspoon.
Chocolate chips: You can use milk chocolate chips, dark chocolate chips, or chocolate chunks in this recipe.