Preheat oven to 375°F. In a large bowl, beat sugar, brown sugar, vanilla extract, butter, and egg with a mixer on medium speed until well combined.

Stir in flour, baking soda, and salt. Mix in white chocolate chips and M&Ms.

Press dough into a 13x9 inch ungreased baking pan. Bake for 20 minutes or until golden brown.

Remove from oven and cool on a wire rack. Cut into squares before serving.