*** Side Note: To roast the bell and poblano peppers: Clean the poblano and bell peppers, then carefully slit them in half, removing the seeds and stem. Line a baking sheet with foil, then place the peppers on top, skin side up. Place the baking sheet on the top shelf of the oven and broil until the peppers are blackened on all sides. Transfer the peppers to a large bowl, cover with plastic wrap, and let cool for 10 minutes. Once the peppers are cool enough to handle, remove the blackened skin VERY CAREFULLY. Chop the peppers up.
Preheat the oven to 375 degrees. Line a baking sheet with foil (for easier clean-up).
Prepare the mushrooms by removing the stems, then drizzle ½ tablespoon of olive oil over each one. Season them to taste with sea salt and freshly cracked pepper. Place them on the baking sheet.
Par-bake the mushrooms by placing them in the oven to bake for 7 minutes.
Prepare the filling by combining the chicken, cumin, coriander, chili powder, oregano, roasted bell and poblano peppers, corn, spinach, tomato, minced garlic, green onions, cilantro, sour cream, and lime juice. Mix well until evenly coated. Taste, then season with sea salt and freshly cracked pepper, to taste.
Carefully remove the mushrooms from the oven. Try not to spill the juice that has collected in the center of the mushroom!
Stuff the mushrooms by spooning the chicken mixture into each mushroom cap (on top of any liquid that has collected in the mushroom).
Sprinkle the top of each mushroom with a bit of shredded extra-sharp cheddar cheese.
Finish baking the mushrooms by placing them in the oven and baking for 10 minutes.
Remove from the oven and serve immediately. Enjoy.