Preheat the oven to 350 and line two baking sheets with parchment or silicone liners.
In a large bowl or the bowl of a stand mixer, cream together the butter, sugar, brown sugar, egg, and vanilla.
Add the flour, pudding mix, baking soda, and salt, and mix to combine.
If the mixture is dry and crumbly, add a teaspoon or two of milk.
Fold in the chocolate chips and M&M candies.
Using a cookie scoop or a tablespoon, drop rounded scoops of dough onto the prepared baking sheets, placing one inch apart.
Bake 8 - 10 minutes, or until lightly golden around the bottom.
Let cool for a few minutes on the baking sheet before removing to a cooling rack.