I would like to make a 3D structure and use something underneath as a mould, but marshmallows do not fit into a lacto-vegetarian diet which I follow.

Does anyone know of anything else one can use?

I am making the hill featured in the movie Nightmare Before Christmas, if anyone is familiar with what I am talking about (:

I have not made them, but vegan rice crispy treats do exist. I googled and found this recipe which got 4.7 out of 5 stars. http://www.healthfulpursuit.com/2012/06/5-ingredient-vegan-rice-crispy-treats/

AA few companies make vegan marshmallows, you should be able to find them at your local Whole Foods. They are pretty expensive though, so if they won't be eaten you can stick to corn syrup or rice syrup.

I have seen the vegan marshmallows, the store is kind of far so next time if I am in a pinch I will try the corn/rice syrup--thanks for the tip!

:D