Heat the oil in a large pot.Add onion, ginger, garlic and sauté for about 5 minutes.Stir in the curry paste and sauté for another 2-3 minutes.In a small bowl, whisk some of the broth together with the almond butter.Add the almond butter mixture, carrots, sweet potatoes and remaining broth to the pot.Bring it to a boil and then turn down the heat to medium and let it simmer for about 20-30 minutes (until potatoes and carrots are soft).Pureé the soup with a hand blender.Season with salt and pepper and lime juice.