Preheat the oven to the broil setting.
In a large Dutch oven over medium-high heat, add 2 tablespoons of the olive oil and saute the onion, poblano, red and yellow bell peppers until soft and lightly caramelized, about 6 minutes. Add the jalapeno, cilantro stems, garlic, chili powder, Southwest Essence, cumin, oregano, and 1 1/2 teaspoons of the salt and cook, stirring, until fragrant, about 2 minutes. Add the tomatoes and vegetable stock, bring to a boil, reduce heat to a simmer and cook for 10 minutes. Add the beans and continue to cook at a simmer until the flavors come together, 30 to 40 minutes longer.
While the chili is simmering, toss the zucchini with 1 tablespoon from the remaining oil and 1/4 teaspoon of the remaining salt and place on a large baking sheet. Broil until caramelized around the edges, 5 to 7 minutes (keep an eye on them, being careful not to burn). Remove from the oven and repeat with the yellow squash, remaining tablespoon of oil and remaining 1/4 teaspoon of salt. Set the zucchini and squash aside to cool while the chili is simmering.
Once the chili has simmered for about 40 minutes, add the zucchini, yellow squash, masa harina, and chopped cilantro and cook for 10 minutes longer. Taste and adjust seasoning, if necessary.
Serve the chili hot, with bowls of the sour cream, Cheddar, green onions and crispy tortilla chips or strips for guests to garnish their bowls, as desired.
Chef's Note: this chili is best made a day in advance.
NOTE # 2: If you are using bouillion for your chicken or vegetable stock, realize that because it contains salt, you may not want to add the full measure of salt as part of your ingredients. Rather taste for salt content at the end of cooking time and add or not according to your preference.
Emeril's Southwest Seasoning:.
Combine all ingredients thoroughly. Yield: 1/2 cup. Store in an airtight container. NOTE: only use 1 tablespoon of the seasoning mix for the chili recipe. The remainder is meant to be stored and used for many other dishes.