Heat the olive oil in a large, heavy-based pot or Dutch oven over a medium heat. Add the chopped onions, carrots, and celery (this combination is known as a mirepoix and is a classic flavour base). Cook for 8-10 minutes, stirring occasionally, until the vegetables have softened and the onion is translucent.

Add the chopped red pepper and minced garlic to the pot. Cook for another 2 minutes until the pepper has softened slightly and the garlic is fragrant.

Stir in the tomato purée, chili powder, ground cumin, smoked paprika, and dried oregano. What works best for me is to cook these spices for about one minute, stirring constantly. This step, known as blooming the spices, really deepens their flavour.

Pour in the tinned chopped tomatoes and the vegetable stock. Scrape any browned bits from the bottom of the pot with your spoon, as this adds lots of flavour. Add the cocoa powder (or dark chocolate) and the optional sugar. Give everything a good stir to combine.

Bring the mixture to a gentle simmer, then reduce the heat to low, cover the pot, and let it cook for at least 30 minutes. This gives the flavours time to meld together. For a richer chili, you can let it simmer for up to an hour.

Add the drained and rinsed black beans, kidney beans, and cannellini beans to the pot. Stir gently and let it simmer, uncovered, for another 10-15 minutes to allow the chili to thicken slightly and the beans to heat through.

Remove the pot from the heat. Squeeze in the juice of one lime and season generously with salt and black pepper to your taste. Let it stand for 5 minutes before serving.

Ladle the vegetarian chili into bowls and garnish with a generous scattering of fresh coriander.