Method
1-Prep the squash: Prep the squash. Preheat the oven to 425 F (220 C). Score the cut sides of the squash in a deep crosshatch and place the halves cut side up in a large roasting dish. Set an onion half, cut side down, into each seed cavity. Want it faster? Peel and cube the squash instead. The smaller you cut everything, the faster it roasts.
2-Load and season the tray: Load and season the tray. Add the bell pepper, carrots, garlic heads (cut side up) and cherry tomatoes around the squash. Drizzle everything with the olive oil, then sprinkle over the cumin, smoked paprika, thyme, rosemary, salt, pepper and chili flakes if using. Rub the seasoning into the squash flesh.
3-Roast for 50 to 60 minutes, until: Roast for 50 to 60 minutes, until a knife slides into the thickest part of the squash with no resistance, the garlic is golden and soft, and the tomatoes have burst. Cubed squash is done in 30 to 35 minutes. If the garlic is still pale, give it 5 to 10 more minutes on its own.
4-Blend: Blend. Let the tray cool for 5 minutes. Scoop the squash flesh out of the skin into a blender, discarding the skin. Squeeze the garlic cloves out of their papers and add them, along with the onion, pepper, carrots, tomatoes and all the juices from the dish. Add 1½ cups of the broth and the ginger if using. Blend until completely smooth, working in two batches if your blender is small.
5-Finish with coconut milk: Finish with coconut milk. Pour the soup into a large pot over medium heat. Stir in the coconut milk and warm through for 3 to 4 minutes. Add more broth until it is as thick or thin as you like it. Taste and adjust the salt.
6-Serve: Serve. Ladle into bowls and top with a swirl of chili oil, a drizzle of coconut milk and chopped herbs. Serve with toasted sourdough.