Preheat the oven to 450°F.
Start by draining the chickpeas (which you've soaked overnight... though I didn't and it was still okay). Place in a saucepan - the chickpeas will expand quite substantially during cooking so make sure you use a large-enough saucepan. They will also cook more evenly if not overcrowded. Cover with 6 cups of water.
Bring to the boil and remove all scum. Add in all the other ingredients for the chickpeas (don't hesitate to use any other leftover bits in the fridge that would be good for the stock). Turn down to a simmer and cook until the chickpeas are tender but not mushy, around 1-1½ hours. At this point, season with salt and pepper.
While the chickpeas are cooking, prepare the squash. I like to cut my squash at different angles for aesthetic reasons, but just make sure they are all a similar size so that they cook evenly. Coat the squash with olive oil, and season. Roast the squash on a high heat to get a lovely caramelisation and colour. Make sure you don't overcrowd the roasting tray as the squash will end up steaming rather than browning. The squash should cook within 25-35 minutes - you want the squash to be cooked through but still holding its shape, otherwise it will go mushy once in the broth.
In another large saucepan, sweat down the onions and garlic in the olive oil over a low heat until soft and sweet - about 10 minutes. Add the red chillies.
Add the rainbow chard stalks and continue to cook on a gentle heat for around 5 minutes until they too soften. Season.
Add the saffron and its liquid. If you have excess saffron strands left in your container, swirl around with a little water and pour in - don't waste any of that delicious flavour.
Add the tinned tomatoes and cook for another 10 minutes until it is slightly reduced.
Now add the cooked chickpeas and their liquid, but remove any stocky bits that were thrown into the chickpea cooking liquid. Bring to a boil and simmer for around 25 minutes.
At this point, add the roasted squash and cook for another 25 minutes, so all the ingredients get to know one another. Season as you go, and at the end, check the seasoning and add enough lemon juice to cut through the richness.
When ready to serve, add the chopped rainbow chard leaves. They will only take a few minutes to cook in the hot broth.
Serve with a drizzle of olive oil.