Humitas are basically vegetarian versions of mexican tamales, and I found this recipe for the filling at a website called Rickcooks.com
This is a sweet and savory, creamy corn filling used in the Chilean tamal called humita, and the casserole called pastel de choclo. It employs a Chilean sweet corn called choclero which I believe is unknown in the U.S. Choclero is distinguished by its stout ears and fat, semi-milky kernels. It is harvested just as the kernels have reached maximum size and turned from white to golden yellow. The popular American sweet corn hybrids are characterized by long, slender ears, and small, very sweet, milky kernels. This recipe has been adapted to account for the extra sweetness and moisture of American sweet corn, primarily by the addition of polenta. (In Chile, the cornmeal, or grits, made from the choclero is called chuchoca, which is Chilean polenta.)
Buy the corn fresh and unhusked, if possible. Reserve the husks for the humitas.
You will have to play with the milk and polenta to acheive the right consistency. It all depends on the moisture content of the corn. Some chocleros are so dry, a cup of milk (and no polenta) will be necessary, while fresh American silver queen may require no milk and up to a cup of polenta. You can even use both, and you won't do any damage.
6 large ears of corn
2 shallots, chopped
8 leaves of fresh basil, finely chopped
1 t salt
3 T butter
½-1 c milk, or
½-1 c polenta or cornmeal, depending on kernel consistency
Remove kernels from ears of corn using a grater. Or cut off kernels with a knife and process very briefly in a food processor (do not liquefy). Melt the butter over medium heat in a large saucepan and sauté the chopped shallots.
Add the corn, chopped basil, and salt, and cook over medium heat, stirring. If the mixture is too dry, add the milk little by little, stirring constantly until the mixture thickens. The amount will depend on the moisture content of the corn. Stop adding milk when the mixture begins to lose consistency.
If too soupy, add the polenta gradually, stirring constantly until the mixture begins to thicken. It should be creamy, not soupy nor thick. Cook over low heat for 5 minutes, let cool, and chill overnight.
Another recipe on the internet added squash, bell peppers and parmesan cheese.