In a large soup pot, melt butter with olive oil. Sauté the onion, ginger and garlic for about eight minutes, stirring occasionally. Add the carrots and stock and bring to a boil. Turn heat down to a simmer and cook until tender for approximately 30 minutes. Turn heat off and let sit until cool enough to blend. If you have a Vitamix blender, now’s your chance to put it to the best use! Blend in batches until smooth and creamy. If you don’t have one, you can either use an immersion blender or traditional blender and blend until smooth. Transfer to a large pot and stir in the light cream. Serve soup hot with croutons.