Preheat the oven to 350℉. Cut the pumpkin in half and remove the seeds (save the seeds if you want to roast them later). Cut the pumpkin halves in half again, and then again, so you have 8 wedges. Line a baking sheet with parchment paper and place the pumpkin wedges on the paper.

Grind the coriander seeds with with a pinch of salt until finely ground. Mix the coriander and salt with the cayenne pepper. Sprinkle the spices over the pumpkin wedges. Then add the black pepper, to taste. Roast the pumpkin fore 1 hour or until really soft and slightly caramelized .

While the pumpkin is cooking, heat a large stockpot and add the oil. Once the olive oil is hot, stir in the onion, garlic, carrot, and celery. Stir for 15 minutes until the veggies are soft, but not mushy.

When the pumpkin is done, remove the tray from the oven and allow to cool for a few minutes. Then scoop out the pumpkin (from the skin) and put into the stockpot with the veggies. Stir in the chicken broth and bring to a simmer and cook for 15 minutes. Then use an immersion blender to blend the soup until smooth. If the soup is too think, add more chicken broth or water. Serve immediately.