Peel and cube the sweet potatoes into 1-inch pieces.
In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until translucent.
Add the minced garlic and grated ginger to the pot and cook for another minute, stirring constantly.
Stir in the red curry paste and cook for an additional minute until fragrant.
Add the cubed sweet potatoes and vegetable broth to the pot. Bring to a boil, then reduce the heat and let it simmer for about 15-20 minutes, or until the sweet potatoes are tender.
Remove the pot from heat and let it cool slightly. Using a blender or immersion blender, puree the soup until smooth.
Return the blended soup to the pot. Stir in the coconut milk, soy sauce, and lime juice. Season with salt and pepper to taste.
Heat the soup over low heat for another 5 minutes, ensuring it does not boil.
Serve hot, garnished with fresh cilantro.