Place butternut squash, red pepper and garlic cloves in a roasting pan, splash over a good drizzle of olive oil and grind over some salt and pepper. Toss to coat well.
Roast in the preheated oven for about 30 minutes, until the squash is tender.
Meanwhile, melt the butter in a large saucepan over a medium heat then add the onion, celery and carrot. Cook and stir until tender, about 8 to 10 minutes.
Remove the roasting pan from the oven and add the roasted vegetables to the saucepan along with any roasting juices and mix well. Pour in the stock and quickly bring to the boil. Reduce heat, cover and simmer for 30 minutes.
Remove from the heat and allow to cool for about 10 to 15 minutes before blending with hand held liquidiser or using a food processor.
Return to a clean saucepan just prior to serving and heat until bubbling. Serve in warmed bowls with a dollop of soured cream.