Slice the carrots in half lengthwise and then into 2 inch chunks.
Pour enough olive oil into the bottom of a heavy stockpot to coat the bottom. Add carrots and onions and saute over medium heat. Cook until the onions start turning translucent.
Turn the heat down, add the garlic and continue cooking another 5 minutes.
Add the ginger and cook another minute or two.
Add the stock and enough additional water to cover the vegetables. Taste and add salt and pepper to your taste. Bring to a boil, then lower the heat to barely simmer.
Add 6 sage leaves (the remaining ones are for garnish). Cook until the carrots are very tender, about 45 minutes.
Remove the sage leaves. Now you need to puree the soup. If you have an immersion blender, use at your own risk. It's hot soup. If using a regular blender, allow the soup to cool, then process in batches and add back to the pot.
Bring the soup back up to a simmer and add the butter, sugar, and lemon juice. You just need the butter to melt. Taste and season again with salt and pepper if needed.
This can be made up to 2 days in advance. Garnish with fresh sage leaves.