Set your slow cooker to low. In a skillet, heat olive oil over medium heat and sauté the diced onion until it turns translucent and fragrant, about 5 minutes.
2 large sweet potatoes
Add the sautéed onion, peeled and chopped sweet potatoes, and carrots into the slow cooker. Pour in the vegetable broth, ensuring that the vegetables are mostly covered.
2 large sweet potatoes
Cover the slow cooker and let the vegetables cook slowly for 6 to 8 hours until they are tender and easily pierced with a fork, filling your kitchen with warm, earthy aromas.
Once cooked, carefully transfer the hot vegetable mixture to a heatproof container and blend it smooth using an immersion blender, or transfer to a standard blender in batches. Blend until the soup has a velvety, consistent texture.
Return the soup to the slow cooker or a pot, season with salt and pepper to taste, and give it a gentle stir. Warm the soup for a few minutes if needed, to ensure it's hot and ready to serve.
2 large sweet potatoes
Serve the soup hot in bowls, garnished if desired with a drizzle of olive oil or fresh herbs, and enjoy the comforting, smooth texture and rich seasonal flavor.