Heat a drizzle of oil in a large, oven-proof fry-pan on medium-high heat. Cook onion for 3–4 minutes, until golden. Add chilli (if using), carrots and capsicum and cook for a further 4–5 minutes, until veggies are soft (add a splash of water if veggies start to stick).
Stir in Mexican spice mix, chilli beans and tomatoes and simmer for about 5 minutes, until sauce has thickened slightly. Season to taste with salt and pepper.
In a small bowl mash avocado with 1–2 teaspoons lemon juice. Season with salt and pepper.
Place a handful of corn chips into each bowl and spoon over the bean and veggie mixture. Top with a small handful of shredded lettuce, mashed avocado, and coriander.