Put the rice into a small pot and rinse with cold water a few times. Discard the cloudy water and add 3 cups of filtered water into the rice. Add the sweet potatoes and bring it to on medium heat. Lower the heat to simmer, cover the pot, and let cook for 45 minutes or until the rice breaks down completely.

If using egg yolk, lightly beat the egg yolk and add to the porridge. Stir a few times, and let cook for about 1-2 minutes. Before serving, use a blender or stick blender to puree the porridge. Serve it cool to avoid burning your baby.