Line a baking sheet with parchment paper or silicone baking mat, like Silpat. Set aside.
In a large mixing bowl, cream butter for 30 seconds. Add both sugars and beat for 3 minutes, until light and fluffy.
Add egg and vanilla and mix until well incorporated.
In another mixing bowl, whisk together flour, pudding mix, cocoa powder soda and salt.
Add the dry ingredients to the butter sugar mixture and mix with an electric mixer until almost incorporated. Switch to a rubber spatula or a wooden spoon, add semi-sweet chocolate chips and M&M's (reserving the white chocolate and some of semi-sweet and M&M's) and stir in until well mixed.
Scoop the cookie dough with a medium (1 and ½ tablespoon) cookie scoop. Roll into balls and place on prepared cookie sheet, spacing them 2" apart.
Press reserved chocolate chips and M&M's onto the balls.
Bake cookies for 9 to 11 minutes (10 minutes was the magic number for me). Cool for 2 minutes on the sheet, then transfer onto a cooling rack to cool completely.