How to Make It
Preheat oven to 375°F. Sprinkle flour evenly on a rimmed baking sheet. Toast in preheated oven 6 minutes. Cool to room temperature, about 10 minutes. Stir in baking soda.
Combine butter, granulated sugar, and brown sugar in the bowl of a heavy-duty electric stand mixer. Beat on medium speed until light and fluffy, 2 to 3 minutes. Add egg and vanilla; beat just until combined. Add toasted flour mixture; beat on low speed until fully incorporated. Stir in chocolate chips and white chocolate chips. Chill at least 1 hour.
Serve cookie dough raw or bake. To make cookies, drop dough by teaspoonfuls onto a baking sheet. Bake at 350°F until browned, 11 to 13 minutes. Cool on baking sheet 5 minutes before serving.