Line a 13"x9" baking pan with parchment paper. 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, 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 chocolate chips and M&M's (reserving some) and stir in until well mixed.
Press the dough onto prepared pan. Add additional M&M's and chocolate chip on top.
Bake bars for 22 to 25 minutes or until the top is golden brown.