Pre-heat the oven to 200 Celcius
Slice the top off of the acorn squash, about an inch from the top. Scoop out the seeds and the fibrous insides and discard. Rub the inside of each with one tablespoon of olive oil and generous cracking of salt and pepper, pop the lid back on top and roast for 45 minutes.
Peel and dice the onion, and add to a frying pan with a splash of oil over medium heat. Cook until onion is soft and translucent - about 10 minutes.
Add the garlic and cook for a further minute or two until fragrant.
Break the broccoli into small florets, add to a food proccesor and blitz until it is in rice sized pieces.
Add the broccoli to the pan with the onion and garlic, crumble in a stock cube and 350ml of hot water. Cook for 5 minutes.
Stir in all remaining ingreidents, except kidney beans and walnuts. Cover and allow to simmer for 15 minutes, stirring occassionally.
Add the kidney beans and roughly chopped walnuts, and cook the chilli uncovered for 5 minutes.
Remove the roasted squash from the oven, and fill with the vegan chilli. Return to oven for 15 minutes.
Remove from oven and serve immediately, with a scattering of coriander over the top.