Heat oil in saucepan over medium heat. Add onion and ginger, cook 5 minutes, or until soft. Add red pepper flakes and cook for 30 seconds.
Add stock and water and bring to a boil. Add sweet potatoes, bring to a simmer and cook 25-30 minutes, until potatoes are soft. Cool 10 minutes.
Transfer mixture to a blender and process until smooth. Return to saucepan and simmer over low heat. Whisk in coconut milk, honey, and cinnamon. Cook until thickened and warmed. Season to taste with salt and pepper.