Pre-heat your oven to 180C (or gas mark 5).
Cook your quinoa according to the packets instructions – most quinoa will cook on the hob with a little water in just 15 minutes. Remove from the heat, drain and set to one side.
While the quinoa is cooking, heat a little oil in a large pan.
Saute the peppers and onion until they have begun to soften, roughly 5 minutes.
Add the chilies, cumin and garlic along with the sweetcorn and beans and cook for a further 5 minutes.
Next add the chopped tomatoes, stir well before adding the quinoa and take off of the heat.
Stir in the sour cream well before transferring to the oven.
Cook the casserole in the oven for 20 minutes, adding the cheese in the last 5 minutes.
Leave to rest for 5 minutes before serving topped with the fresh coriander and diced cubes of avocado.