In a large pot, heat the olive oil over medium heat. Add the chopped onion and minced garlic. Sauté until the onions are translucent, about 5 minutes.

Stir in the cubed sweet potatoes and chopped red bell pepper. Cook for another 5 minutes to soften them slightly.

Pour in the vegetable broth, ensuring all the vegetables are covered. Increase the heat to bring it to a boil, then lower it to a simmer. Cover and let it cook for about 15-20 minutes, or until the sweet potatoes are fork-tender.

Remove the pot from heat. Use an immersion blender to purée the soup until smooth. Alternatively, carefully transfer it in batches to a standing blender, blending until creamy.

Return the blended soup to the pot over low heat. Stir in the coconut milk, seasoning with salt and pepper to taste. Allow it to heat through.

Serve the soup hot, garnished with fresh herbs and red pepper flakes if desired.