1 - Gently fry the onion and the garlic in a deep saucepan over a low heat for 8-10 minutes, until soft and translucent.
2 - Drain the ancho chilli, cut in half, remove stalk and seeds and finely chop. Add the chilli to the pan, along with the paprika and cumin, stir and cook for a further 1-2 minutes until fragrant.
3 - Increase the heat to medium, add the tinned tomatoes and vegetable stock and bring to the boil. Reduce the heat and simmer for 15 minutes.
4 - Meanwhile pre-heat the grill and brush the corn on the cob with a little olive oil. Grill for 5 to 8 minutes, taking care that the cobs do not burn, until they are golden and slightly charred. Allow to cool slightly and then slice the kernels from the cob and put to one side.
5 - Pre-heat the oven to 200C/180C fan/Gas 6.
6 - Add the sweetcorn kernels to the soup along with the black beans. Cook for 5 minutes more. Season to taste with salt and pepper.
7 - Place the tortilla triangles on a large oven tray in a single layer and brush both sides with a little olive oil. Put into the pre-heated oven and toast for 5 minutes. Keep an eye on them as they burn easily. Once toasted, take them out and cut into small triangles.
8 - Make the salsa by adding the avocado, lime juice, chilli and coriander to a bowl, along with a drizzle of extra virgin olive oil. Season with salt and pepper and stir to combine.
9 - To serve, ladle the soup into warmed bowls and add a dollop of salsa, sour cream (optional) and a few tortilla chips. Sprinkle over some extra coriander, add a drizzle of extra virgin olive oil and serve.