In a large saucepan over low heat, add sweet potatoes, water, thyme, sugar, and 1/2 teaspoon salt. Cover and cook until the potatoes fall apart easily and all the water has been absorbed, about 25 to 30 minutes.
Mash the potatoes until just a few lumps remain. Stir in the half-and-half and butter and season to taste with salt and pepper.
Sweet potatoes: Use orange, white or purple sweet potatoes. What about yams? At most grocery stores, yams and sweet potatoes are the same. Years ago, farmers renamed the potatoes to "yams" as a marketing schtick. True yams have bark-like skin and much more starch content similar to a Russet potato.
Thyme: Fresh (or dried) thyme taste great with sweet potatoes. You could also try garlic, parsley, rosemary, or sage.
Half-and-half: I recommend half-and-half for this recipe, and not substituting sour cream.
Yield: This recipe makes about 5 cups of mashed sweet potatoes, enough for 4 generous servings, 1 ¼ cups each.
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: Peel and cube the raw potatoes up to 24 hours in advance. Cover with water and chill in the refrigerator.
Freezer: Cool the mashed sweet potatoes completely, then spoon them into a freezer-safe container. Label, date, and freeze for up to 1 month.
Meal prep: Mashed sweet potatoes make a great side dish for weekly meal prep, if you're into that (you may want to omit the sugar).
Peel before boiling: They'll cook much faster without the peel. Boiling sweet potatoes whole with skin takes a lot longer, and needs more water. I also slice them to speed up the cooking time.
For chunky, rustic-style mashed sweet potatoes: Use a basic potato masher. A waffle-head masher will mash the potatoes into a smoother consistency, if you like them somewhere in-between.
For super-smooth mashed sweet potatoes: Use a potato ricer (peeled potatoes) or food mill (unpeeled potatoes). These gadgets make the smallest, finest pieces of cooked potato, which fluff up beautifully.
Classic mashed potatoes: For the classic version without the secrets, try my best mashed potatoes recipe.
Boursin mashed potatoes: Soft-skinned small red potatoes mixed with fresh herbs and a block of Boursin cheese. You don’t even have to peel the potatoes!
Slow cooker: Once the mashed sweet potatoes are ready, you can put them in a crock pot and heat on the LOW setting to keep them warm and fluffy throughout your feast. I have never found a mashed potato recipe MADE in a slow cooker that I thought tasted good.