01 - Roast or steam the Korean sweet potato until completely tender, approximately 20 to 25 minutes. Allow to cool briefly, remove skin, and cut into 1-inch pieces.
02 - Combine prepared sweet potato, milk, sweetener if using, and vanilla extract in a blender canister. Process on high speed for 60 to 90 seconds until completely smooth and creamy, with no visible lumps.
03 - Transfer blended mixture to a small saucepan. Warm over medium-low heat, stirring occasionally, until steaming hot but not boiling, approximately 3 to 5 minutes. Divide evenly between two heated mugs. Dust with cinnamon or nutmeg if desired and serve immediately.