Set a 4-quart stock pot over medium-high heat. Add the butter and olive oil to the pot. Once the butter is melted, place the onions and celery in the pot. Sweat the vegetables until the onions are translucent, about 3 to 4 minutes. Add the ginger and garlic to the pot and cook for 30 seconds. Place all of the carrots in the pot and cook, stirring occasionally, until the carrots are lightly caramelized and start to soften, about 7 to 8 minutes. Add the stock, salt, pepper and bay leaf to the pot and bring to a boil, then reduce to a simmer. Cook the soup until the carrots are tender, about 20 to 25 minutes.

Remove the bay leaf from the pot and using an immersion blender puree the soup directly in the pot or in batches in a bar blender. Adjust the seasoning, add the heavy cream to the pot.

To serve, garnish with 1 tablespoon of sour cream per serving and a sprinkling of fresh chives.