From America's Test Kitchen
Mashed sweet potatoes often turn out overly thick and gluey or, at the other extreme, sloppy and loose. We wanted a recipe that would push sweet potatoes’ deep, earthy sweetness to the fore and that would produce a silky puree with enough body to hold its shape on a fork.
We braised the sweet potatoes in a mixture of butter and heavy cream to impart a smooth richness. Adding a little salt brought out the sweet potatoes’ delicate flavor and just a teaspoon of sugar bolstered their sweetness. Once the potatoes were tender, we mashed them in the saucepan with a potato masher. We skipped the typical pumpkin pie seasoning and instead let the simple sweet potato flavor shine through.
Cutting the sweet potatoes into slices of even thickness is important in getting them to cook at the same rate. A potato masher will yield slightly lumpy sweet potatoes; a food mill will make a perfectly smooth puree. The potatoes are best served immediately, but they can be covered tightly with plastic wrap and kept relatively hot for 30 minutes. This recipe can be doubled in a Dutch oven; the cooking time will need to be doubled as well.