In electric mixer bowl, cream together butter and sugar. Mix in egg and vanilla until smooth. Add pudding mix, baking soda, and salt; mix until combined. Stir in flour, then stir in sprinkles and M&Ms™
. Scoop dough in 2-tbsp balls onto a cookie sheet or platter covered with parchment or a silicone baking mat. Cover and chill for at least 30 minutes. Preheat oven to 350 degrees F. Line cookie sheets with parchment paper or Silpat® baking mats. Arrange chilled cookie dough balls on cookie sheets, 2” apart. Bake 9 to 11 minutes or until the edges just start to turn brown. Cool on cookie sheet for 5 minutes before transferring to a rack to cool completely.