Preheat oven to 375°F. In a large bowl, beat sugar, brown sugar, vanilla extract, softened butter, and egg with a mixer on medium speed until well combined.
Stir in flour, baking soda, and salt until just combined. Then fold in white chocolate chips and pastel M&Ms.
Press cookie dough evenly into an ungreased 13 x 9 inch baking pan.
Bake for 20 minutes or until the top is golden brown.
Remove from oven and place on a wire rack to cool completely before cutting into squares.
Notes
These delicious cookie bars store well in an airtight container for up to a week and are perfect for Easter or springtime gatherings.