Preheat the oven to 350°F (180°C).
Cream together the butter, both sugars, egg and vanilla.
In a separate bowl, sift together the flour, salt and baking soda.
Mix the dry ingredients with the creamed mixture. Mix well.
Scoop into balls and then roll in mini M&M's. Press the M&M's into the cookie dough ball.
Bake at 350°F (180°C) for 9-11 minutes or until the tops are no longer glossy.
Best if eaten the same day but will stay fresh for a couple of days in an airtight container.
