Peel the yams, cut them into similar sized 1”-2” pieces and place them in a pot of cold salted water.
Bring the water to a boil and cook for 20-35 minutes or until fork-tender.
Drain and let steam evaporate for at least 5 minutes.
Purée in blender until smooth, in 2-4 batches, depending on the size of your blender. Add cream, butter, and cinnamon to each batch, enough to achieve a creamy consistency – this will depend on which type of yam you use and how starchy they are. Make sure to wear oven gloves to guard your hands against the hot steam that will come out of the yams as they’re puréed.
Once the batches are finished, add additional butter or cream as needed to even out consistency. Be careful not to add too much cream, or you’ll end up with a soupy texture.