Heat oil in a heavy-based pan and cook onion and garlic until onion is soft.
Add tomatoes,jalapenos,cumin,salt and sugar,mixing well.
Add stock and simmer gently,partly covered,for 10 minutes.
Add kidney beans and corn and simmer for a further 10 minutes.
Heat oven to 180C,or use an overhead grill.
Shred chicken and set aside with avocado and coriander for serving.
Arrange corn chips on kitchen foil,scatter with grated cheese (and extra chopped jalapenos if you like it hot) and bake or grill until cheese melts.
To serve: Divide broth and beans between four warmed,shallow soup plates. Arrange shredded chicken in the centre and top with avocado,nachos,coriander and remaining cheese.