Cut huitlacoche off corncob and dice. Heat a medium saute pan with oil, add onions cook until soft. Add huitlacoche saute until tender, about 5 minutes.
In a medium bowl combine the masa harina, water, and salt and stir until smooth.
The dough should be slightly sticky and form a ball when pressed together. To test, flatten a small ball of dough between your palms. If the edges crack, add water, a tablespoon at a time until a test piece does not crack.
Place a small ball of dough between two pieces of waxed paper and press or roll into a small tortilla.
Folding the raw dough, make a pocket, and fill with a tablespoon each of Sauteed huitlacoche and queso blanco. Seal the edge. Cook on grill for 5 minutes until golden brown.