Heat grill to medium high. Lightly brush vegetables (mushrooms, onion, poblano pepper, and corn) with olive oil. Grill over direct medium heat, turning occasionally and with lid closed, about 8-10 minutes, or until the poblano chile pepper is blackened and blistered all over and the vegetables are tender.

Remove vegetables from the grill to cool; place the chile in a bowl and cover with plastic wrap to make removing skin easier.

Coarsely chop the onion and place in a separate bowl. Chop mushrooms and cut corn from cob. Scrape skin from chile, remove the seeds and stem, and dice.

In a large saucepan, heat the chicken broth until it simmers. Keep warm.

Melt the butter in a large skillet on high heat. Sauté the onion and rice, 2-3 minutes, stirring often. Rice should be slightly opaque. Add one cup of the simmering broth and stir until the liquid is absorbed.

Continue adding one cup at a time of the hot broth, cooking until the broth is absorbed before adding the next cup. Rice will become tender after about 20-30 minutes, and should be creamy, with no liquid. Add the remaining vegetables and salt.

Remove from heat and stir in the parmesan cheese until melted.