Heat olive oil in a large Dutch oven or heavy-bottomed stockpot over medium heat. Add diced onion and cook for 5-7 minutes, until softened and translucent.

Stir in minced garlic and jalapeño (if using) and cook for another 1 minute until fragrant. Be careful not to burn the garlic.

Add diced red and green bell peppers to the pot and cook for 3-5 minutes, stirring occasionally, until slightly softened.

Add chili powder, cumin, smoked paprika, dried oregano, and cayenne pepper (if using) to the pot. Stir well to coat the vegetables and cook for 1 minute until fragrant. This 'blooming' of spices enhances their flavor.

Stir in the tomato paste and cook for 2-3 minutes, stirring frequently, until it darkens slightly and caramelizes on the bottom of the pot.

Pour in the rinsed dry lentils, diced tomatoes (undrained), crushed tomatoes (undrained), and vegetable broth. Stir everything to combine.

Bring the chili to a boil, then reduce heat to low, cover, and simmer for 30 minutes, or until the lentils are tender, stirring occasionally to prevent sticking.

Stir in the rinsed and drained kidney beans, black beans, frozen corn, unsweetened cocoa powder, and apple cider vinegar. Continue to simmer, uncovered, for another 10-15 minutes, allowing the flavors to meld and the chili to thicken.

Season with salt and black pepper to taste. If the chili is too thick, add a splash more vegetable broth or water. If it's too thin, simmer uncovered for a few more minutes.

Ladle the hearty vegan chili into bowls and serve hot with your favorite toppings such as diced avocado, fresh cilantro, a squeeze of lime, a dollop of vegan sour cream, or a sprinkle of vegan shredded cheese.