In a large bowl or stand mixer fitted with a paddle attachment, cream the butter and sugars together until smooth. Scrape down the sides of the bowl, if needed.
Add the pudding, eggs, additional egg yolk, vanilla, and imitation butter. Beat for about one minute on medium speed.
In a separate bowl, combine flour, baking soda, and salt.
Add the dry ingredients to the wet ingredients a 1/2 cup at a time and mix until combined.
Mix in the toffee chips.
Form the dough into a giant ball and wrap tightly in plastic wrap. Chill the dough for at least two hours. Remove the dough a little while before baking so the dough can soften a bit and is easier to work with.
Scoop the dough using a medium cooking scoop and roll the dough between your hands to form round balls of dough and place onto a nonstick baking sheet about two inches apart. Top with yellow sprinkles, if desired.
Bake at 350 F for 10-13 minutes.
Cool on the pan for a couple of minutes before transferring to a cooling rack.