Heat 2 tablespoons coconut oil in a large stock pot or Dutch oven over medium-high heat. Add the onions, carrots, and sweet potato and cook, stirring occasionally, until the onions are soft and translucent, about 5 minutes. Add the garlic and ginger and cook, stirring, for another minute. Add the curry paste and cook, stirring, for 1-2 minutes or until fragrant. Add the vegetable broth, coconut milk, and ½ cup Sunbutter. Bring to a boil, then simmer, uncovered, until the vegetables are tender, 15-20 minutes. Working in batches if needed, puree the soup in a blender until smooth. Return to the pot and keep warm.
Lightly toast the bread. Spread 2 slices with Sunbutter and the other 2 with the sweet chili sauce. Sandwich together.
Heat the remaining coconut oil in a skillet over medium heat. Add the sandwiches and cook on each side until golden brown, about 1-2 minutes per side. Let cool slightly then cut into small squares.