In a large, heavy pot, brown turkey, onions, garlic, and bell peppers, and cook, stirring, until meat is browned completely. Add the zucchini, corn, and mushrooms, and cook, stirring, until soft and the vegetables give off their liquid and start to brown around the edges, about 6 minutes. Add the chili powder, cumin, salt and cayenne, and cook, stirring, until fragrant, about 30 seconds. Add the tomatoes and stir well. Add the beans, tomato sauce, and vegetable stock, stir well, and bring to a boil. Reduce the heat to medium-low and simmer, stirring occasionally, for about 20 minutes.

Remove from the heat and stir in the cilantro. Adjust the seasoning, to taste.

To serve, ladle the chili into the bowls. Top each serving with a dollop (~1oz) of yogurt and spoonful of avocado. Sprinkle with green onions (and optional 1 oz cheddar cheese) and dig in!