Cream butter and sugars in the bowl of a stand mixer fitted with the paddle attachment. Cream until light and fluffy. You can also use a hand mixer. Add oil and stir until smooth. Add egg and vanilla, mix until smooth, then stir in the salt and baking soda.
Mix in oats and flour until just mixed. Stir in coconut and cornflakes, then stir in chocolate chips.
Scoop 2 tablespoon balls of cookie dough onto a cookie sheet covered in wax or parchment paper. No need to spread the balls out, you’re just going to chill them. Cover with plastic wrap and chill at least one hour. (If you chill longer than 4 hours you may need to let them warm up a few minutes on the counter before baking.)
Preheat oven to 350°F. Line cookie sheets with parchment paper or silpat baking mats. Place cookies 2” apart on prepared cookie sheets. Lightly press down with the palm of your hand. Bake for 9-11 minutes or until the bottoms just start to turn golden brown. Cool at least 5 minutes on cookie sheet before removing to rack to cool completely.
Store in an airtight container for up to 5 days or freeze for up to 1 month.
I love using Trader Joe's Chocolate Chips for the most gooey cookies!