Cream butter and sugars in a large bowl or stand mixer fitted with a paddle attachment. Mix until light and fluffy, about 2 minutes.
Add the egg, additional egg yolk, pudding mix, and vanilla extract to the mix and beat until well blended.
Add the graham crackers to a food processor and pulse until fine crumbs form.
In a large bowl, add graham cracker crumbs, flour, baking soda, and salt and whisk together.
Slowly add the dry ingredients to the wet ingredients a little at a time and beat until well combined.
Fold in the chocolate chunks and mallow bits.
Wrap up and chill for at least two hours. Use a medium cookie scoop to portion out cookies on a parchment-lined baking sheet.
Bake the cookies at 350 degrees F for 11 to 13 minutes until edges are golden brown.
Let the cookies cool on the pan for a minute or two before transferring to a cooling rack to cool completely.