Yes, twinkies taste chemical and you can be sure there would be no cream or butter. But i remember twinkies from when i used to eat them in the 1950s and they have also changed over time.
I have a recipe somewhere for a whoopie pie filling that is made by cooking a thick flour, sugar and milk mixture (like a choux base with lots of sugar, before the eggs are added), letting it cool then beating in shortening (you could use butter for better flavor but it won't be white) and it was not bad. so just flour, milk, sugar and then shortening or butter.
I remember it being very much like the fillings twinkies, devil dogs and other junk foods of the 50s. Not bad at all, actually.
I can look it up if you're interested.