Mashed Sweet Potatoes
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Whenever I have extra sweet potatoes on hand, I turn them into Mashed Sweet Potatoes with rosemary butter for herby warmth, sweet caramelized onions, and a salty finish from Parmesan. There’s one simple step at the end that helps the topping melt in perfectly, and you’ll taste why it matters.
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Mashed Sweet Potatoes make a perfect side dish for everything from Thanksgiving and Christmas dinners to Sunday meals and holiday potlucks. You can make them ahead, stash them in the fridge, or freeze them for easy prep. It’s the kind of side that always earns a spot on the table.
Ingredients You’ll Need
You’ll need all the ingredients shown in the photograph below.
How to Make Mashed Sweet Potatoes with Step-By-Step Instructions
Scroll down for the full recipe card containing a full printable recipe and measurements in both US customary and metric units.
You’ll find this dish easy to prep if you follow my simple steps from start to finish.
Caramelize the Onions
Heat the olive oil in a skillet over medium heat. I like using this large nonstick skillet like this one to give the onions enough space to cook down evenly without burning.
Add the sliced sweet onions and cook, stirring often, for 20 to 30 minutes until soft, golden, and slightly jammy. A mandoline slicer makes it faster and safer to get even slices with less mess.
Stirring regularly with my flexible silicone spatula avoids the onions from sticking and helps you scrape up any browned bits. Keep the heat steady so the onions caramelize slowly rather than brown too quickly.
In the last minute of cooking, sprinkle in the salt and pour the maple syrup to enhance their natural sweetness and deepen the flavor. Let the onions absorb the syrup, then remove from the heat and set aside.
Boil the Sweet Potatoes
Throw in the peeled and cubed sweet potatoes to a large pot and cover with water by about an inch. This stainless steel saucepan works well here because it holds everything without scorching.
Using a vegetable peeler speeds up the prep of the sweet potatoes. Then I chop them into chunks with my sharp chef’s knife so I can control the cuts.
Bring it to a boil, then lower the heat to medium and cook for 12 to 15 minutes or until fork-tender. Avoid overcooking to prevent them from becoming waterlogged.
Make the Rosemary Butter
In a small microwave-safe bowl, combine the butter and finely chopped fresh rosemary. A small prep bowl is perfect for this step, and you can reuse it later to store extra herbs or butter.
Microwave it for 30 to 45 seconds, so the butter is fully melted and begins to release a warm, herby aroma. This quick step adds a subtle depth that really complements the sweetness of the potatoes.
Mash and Mix
Drain the cooked sweet potatoes and return them to the pot. I drain the sweet potatoes using this stainless steel colander to avoid splashing and to let the steam escape quickly.
Mash them to your desired consistency using a hand masher or large fork. I keep a potato ricer in my drawer just for recipes like this; it gets the job done without overworking the texture.
Stir in the rosemary butter, milk, and salt until smooth and creamy.
Assemble and Bake
Spoon the mashed sweet potatoes into a baking dish. I always reach for my ceramic baking dish because it heats evenly and looks good enough to serve straight from the oven.
Make sure the surface is silky so the toppings sit nicely. Spread the caramelized onions over the top, then sprinkle with Parmesan cheese.
Bake at 325°F (160°C) for about 5 minutes, just until the cheese melts and turns lightly golden. This oven thermometer ensures the temperature stays on point. You don’t want to overbake, just enough to warm everything through and let the flavors come together.
Serve and Garnish
Once the cheese is melted and lightly golden, remove the dish from the oven. Add a fresh rosemary sprig on top for a simple garnish, then serve warm right from the baking dish.
Finally, enjoy your Mashed Sweet Potatoes!
If you’re taking this to a gathering or holiday meal, I always cover the baking dish with a stretchable silicone lid that seals well and won’t slide off in the car. If I’m bringing individual servings or need to prep portions ahead, I pack them in this portable container with a snap-on lid so they’re easy to stack, reheat, or hand out.
To keep everything warm until serving, I tuck it inside my insulated casserole carrier, which works especially well for potlucks or buffet tables.
Ingredients
For the Onions:
- 1 cup sliced sweet onion
- 2 tablespoons olive oil
- ½ teaspoon salt
- 1 tablespoon maple syrup
For the Sweet Potatoes:
- 3 pounds sweet potatoes peeled and cubed
- ¼ cup butter
- 1 tablespoon fresh rosemary finely chopped
- ½ cup milk
- 2 teaspoons salt
- ½ cup grated Parmesan cheese
- Fresh rosemary sprigs for garnish
Video
Instructions
- Heat olive oil in a skillet over medium heat. Add the sliced onions and cook for 20 to 30 minutes, stirring often, until soft and golden brown.1 cup sliced sweet onion, 2 tablespoons olive oil
- In the last minute of cooking, add the salt and maple syrup, stirring to coat. Set aside.½ teaspoon salt, 1 tablespoon maple syrup
- Place the cubed sweet potatoes in a large pot and cover with water, about 1 inch above the potatoes. Bring to a boil over high heat, then reduce to medium heat and cook for 12 to 15 minutes, or until fork-tender.3 pounds sweet potatoes
- In a small microwave-safe bowl, combine butter and chopped rosemary. Microwave for 30 to 45 seconds until the butter melts. Let it sit for a few minutes to infuse the flavor.
- Drain the sweet potatoes well and return them to the pot. Mash with a potato masher or large fork to your desired texture.
- Stir in the rosemary butter, milk, and salt until smooth and creamy.¼ cup butter, 1 tablespoon fresh rosemary, ½ cup milk, 2 teaspoons salt
- Spoon the mashed sweet potatoes into a baking dish. Top with the caramelized onions and sprinkle with Parmesan cheese.½ cup grated Parmesan cheese
- Bake at 325°F (160°C) for about 5 minutes, or until the Parmesan cheese is melted and lightly golden.
- Top with a fresh rosemary sprig before serving.Fresh rosemary sprigs
Notes
- Slice the onions thinly: Thin slices caramelize more evenly and soften nicely during the slow cook.
- Don’t rush the onions: Let them take their time on medium heat so they develop a rich, sweet flavor without burning.
- Cut the sweet potatoes evenly: Uniform cubes cook faster and more evenly, saving you time and guesswork.
- Infuse the butter properly: Let the rosemary sit in the melted butter for a few minutes before using; it deepens the herby, buttery flavor throughout.
- Mash to your liking: Use a fork for a rustic texture or an electric hand mixer if you prefer it completely smooth.
- Don’t skip the salt: Sweet potatoes can taste flat without enough salt. Taste as you go.
- Customize the flavor: Black pepper adds subtle depth, or go festive with a hint of cinnamon or brown sugar, and add fresh herbs.
Nutrition
How to Store Leftovers
Let the mashed sweet potatoes cool to room temperature, then wrap them tightly in plastic wrap or foil or transfer them to an airtight container and refrigerate for up to 3 days. I use this plastic wrap because it clings tightly and keeps everything fresher longer. Heavy-duty aluminum foil also works well to prevent refrigerator smells from creeping in.
I use glass containers with locking lids to keep the leftovers fresh and easy to reheat in the same dish.
You can also freeze them, though the texture may soften slightly once thawed. For freezing, store in a freezer-safe container for up to one month. This freezer-safe glass container with locking lids with tight-fitting lids helps prevent freezer burn and keeps things tidy in the freezer.
Reheat in the oven or microwave until warmed through, adding a splash of milk to loosen the texture if needed.
What to Serve With Mashed Sweet Potatoes
Mashed sweet potatoes are right at home with vegetarian mains like lentil loaf, chickpea patties, or a savory mushroom pie. They also pair beautifully with sides like roasted Brussels sprouts, sautéed green beans, or a crisp celery salad. For holiday dinners, serve them with stuffing, cranberry sauce, and cozy casseroles to round out the table.
More Easy Potato Recipes for You to Try at Home
I’ve got more cozy and crowd-pleasing potato sides that come together just as easily as this one.
(2) Fabulous recipes. Sweet Potatoes & Mashed Parsnips. I could make a meal out of both of those!! Yummm!!