Preheat oven to 400 degrees Fahrenheit.
Heat 3 tablespoons of butter on medium heat. Once it is warm and bubbling, add the minced garlic and sauté for 2 minutes.
Add the onions, mushrooms, salt, pepper, and sauté until the onions are translucent and the mushrooms are soft and creamy, about 5 minutes.
Add the spinach and cook until just wilted.
Add the rice and toss to coat. Add the diced tomatoes, fire-roasted diced tomatoes, and chicken broth into the pan and bring to a simmer. Reduce heat to medium-low and cook for 20 to 25 minutes until the rice is done and the liquid has been reduced.
While the filling simmers, make lengthwise slits in the poblano peppers and carefully remove the pith and seeds, being careful not to rip the peppers.
Turn off the heat and mix the goat cheese into the mixture.
Stuff the peppers with the filling. Sprinkle each with 1 to 2 tablespoons of the corn salad and some cotija cheese.
Bake for 15 to 20 minutes. Let cool for a few minutes and then serve with a topping of the Mexican Corn Salad.