Preheat oven to 350 degrees. Rub mushrooms with 2 T olive oil inside and out, sprinkle with a pinch of salt and pepper and place on a baking sheet, gills side up. Heat the remaining 2 T oil in a non-stick skillet, add cornbread cubes and sauté until golden brown and crispy, approx. 5 min. Remove from heat.
In a bowl, combine the rest of the filling ingredients. Add cornbread and toss gently. Do not overwork or cornbread will crumble and filling will become dense. Taste and adjust seasonings. Mound the mixture onto the prepared mushroom caps. Bake for 8-10 min, until the cheese melts and mushrooms soften.
Garnish with Chipotle Lime Sauce, crumbled queso fresco and chopped green onion. Serve with a fresh green salad.
Chipotle Lime Sauce
Mix sauce ingredients in a small bowl and set aside. Drizzle sauce over baked mushrooms when ready to serve.