Peanut Butter Butterscotch Skillet Cookies

all-purpose flour 1/4 tsp. baking soda 1/8 tsp. kosher salt 1/4 cup creamy peanut butter (I used honey-roasted) 1/4 cup butter, room temperature 1/2 cup packed light brown sugar 1/4 cup granulated sugar 1 egg 1/4 cup butterscotch chips