01 - Preheat oven to 350°F. Line baking sheets with parchment paper.
02 - Whisk together flour, baking soda, and salt in a medium bowl until well blended.
03 - Beat butter, granulated sugar, and brown sugar in a large bowl until creamy and fluffy.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in vanilla extract.
05 - Gradually add dry ingredients to wet mixture, mixing until just combined. Do not overmix.
06 - Gently fold in mini marshmallows, crispy rice cereal, and white chocolate chips until evenly distributed.
07 - Drop dough onto prepared baking sheets using a cookie scoop, spacing 2 inches apart.
08 - Bake for 10 to 12 minutes, until edges are golden brown and centers are just set.
09 - Let cookies cool on baking sheets for 5 minutes, then transfer to wire rack to cool completely.