In a large pot or Dutch oven, melt the butter over medium heat. Add the onion, carrot and celery. Cook for 5-7 minutes, until onions are just soft.
Stir in butternut squash, ginger and curry powder. Cook for another 3 minutes.
Pour in the vegetable broth and bring to a boil over high heat. Cover and reduce to a simmer. Continue to simmer for 20 minutes, or until the squash and carrots are soft.
Use an immersion blender to puree the soup, or work in batches and transfer to a standing blender or food processor to puree, returning back to the pot.
Stir in the apple butter until fully combined. Season with salt and pepper to taste. Serve hot. Store leftovers in the fridge for up to 3 days.