Preheat oven to 400°.
Arrange halved squash, garlic, and onions in a single layer on a large baking sheet. Drizzle with olive oil and sprinkle with paprika, thyme, rosemary, pepper, and salt.
Roast in the oven for 35-40 minutes or until squash is tender.
Remove from oven and let cool for 4-5 minutes until cool enough to handle.
Scoop out squash and add to a mixer, along with the onion halves, and the roasted garlic. Blend until combined.
Add vegetable broth into mixer and blend until fully incorporated.
While the squash is roasting, melt the butter in a large pot or dutch oven. Add the diced celery and carrots, and saute until they're tender.
Pour squash mixture into the large pot with the vegetables. Cook on low/medium heat for 10-15 minutes.
Stir in heavy cream and add salt and pepper if needed.
Continue to cook over low/medium heat for an additional 5-10 minutes.
Serve hot and enjoy.