Note: this dough requires chilling.
Cream butter and sugars in the bowl of a stand mixer fitted with the paddle attachment. 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 chocolate chips and Frosted Flakes cereal. There is no need to crush the cereal; a stand mixer will do that for you. If you’re using a hand mixer, you may want to crush the cereal into large pieces before adding it to the cookie dough.
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. 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.
Serve as is or make ice cream sandwiches with vanilla ice cream and crushed Frosted Flakes!
Store in an airtight container for up to 5 days or freeze for up to 1 month.