01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk together flour, baking soda, and salt in a medium bowl. Set aside.
03 - Beat softened butter, brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
04 - Beat in eggs one at a time, then mix in vanilla extract until fully incorporated.
05 - Gradually add flour mixture to wet ingredients, mixing on low speed until just combined.
06 - Gently fold in M&M candies and white chocolate chips by hand.
07 - Scoop dough balls onto prepared baking sheets, spacing 2 inches apart. Press extra M&Ms and decorations onto tops.
08 - Bake for 9-11 minutes until edges are set and centers appear slightly underbaked.
09 - Let cookies rest on baking sheets for 5 minutes, then transfer to wire rack to cool completely.