Heat 1 tbsp olive oil in a large Dutch oven or stockpot over medium-high heat. Add the finely chopped cremini mushrooms and walnuts. Sauté, stirring occasionally, for 8-10 minutes, until most of the moisture from the mushrooms has evaporated and they are browned, and the walnuts are lightly toasted. Stir in 1/2 tsp smoked paprika, 1/4 tsp garlic powder, a pinch of salt, and a pinch of black pepper. Remove from the pot and set aside.

Add 2 tbsp olive oil to the same pot over medium heat. Add diced yellow onion, red bell pepper, and green bell pepper. Cook, stirring occasionally, for 8-10 minutes until softened.

Stir in the minced garlic and optional minced jalapeño. Cook for another 1-2 minutes until fragrant, being careful not to burn the garlic.

Stir in the tomato paste and cook for 1 minute, stirring constantly, to deepen its flavor. Add the crushed tomatoes, tomato sauce, vegetable broth, and apple cider vinegar. Bring to a gentle simmer.

Stir in the 3 tbsp chili powder, 2 tsp ground cumin, 1 tsp smoked paprika, 1/2 tsp dried oregano, and optional 1/4 tsp cayenne pepper. Mix well to combine all the spices.

Drain and rinse all three cans of beans thoroughly. Add the rinsed beans and frozen corn to the pot. Stir in the reserved mushroom and walnut crumble.

Bring the chili back to a gentle simmer, then reduce the heat to low, cover, and let it cook for at least 30 minutes, or up to 1 hour, stirring occasionally. The longer it simmers, the more the flavors will meld.

After simmering, taste the chili and adjust seasonings as needed, adding more salt, pepper, or chili powder to your preference. If it's too thick, add a little more vegetable broth. If too thin, simmer uncovered for a bit longer.

Ladle hot chili into bowls and serve with your favorite vegan toppings like fresh cilantro, diced avocado, a dollop of vegan sour cream, or crushed tortilla chips.