Preheat oven to 350 degrees Fahrenheit. Line cookie sheets with nonstick baking mats or lightly spray them with nonstick cooking spray.
In the bowl of an electric mixer, cream together butter, granulated and brown sugars, vanilla and eggs.
In a separate bowl, whisk together salt, baking soda, baking powder and flour.
Add flour mixture to the wet mixture and mix just until incorporated. Dough will be slightly sticky.
Scoop dough by 1/8 cupfuls, then roll it around in your hands to form a ball and place on cookie sheets 2" apart.
Bake for about 10 minutes. Be careful not to overbake!
As soon as the cookies are out of the oven, press about 6 Christmas M&M's into the top of each cookie to make them extra pretty.
Let cookies sit on cookie sheets for a few minutes, then carefully remove them to a cooling rack to cool completely. Store in an airtight container or bag.