Slow-Cooker Sweet Potato Casserole with Marshmallows Step-by-step instructions

Before you start

Before starting, peel and cube the sweet potatoes into 1-inch pieces. Measure the brown sugar, butter, vanilla, cinnamon, and nutmeg so they are ready to add. If using candied pecans, have them measured and set aside.

Make sure the slow cooker is clean and dry. No need to preheat anything; the slow cooker will do the work. This recipe can be assembled in the morning and left to cook, but the marshmallow topping should be added only during the last 15 minutes of cooking.

Instructions

Layer and Cook

1. 1Layer the Sweet Potatoes
   Place the cubed sweet potatoes in a 6-quart slow cooker. Add the brown sugar, melted butter, vanilla extract, cinnamon, and nutmeg. Stir gently to coat every cube evenly.
   Look for The sweet potatoes are glossy with butter and sugar, and the spices smell warm.
   Tip Cut the sweet potatoes into even 1-inch cubes so they cook at the same rate.
2. 2Cover and Cook
   Cover the slow cooker and cook on HIGH for 3 1/2 hours, or until the sweet potatoes are very tender when pierced with a fork. Stir once halfway through if possible.
   Look for The sweet potatoes are fork-tender and the liquid is bubbling around the edges.
   Tip Resist lifting the lid often; the heat escapes and extends the cooking time.

At the end of this phase, the sweet potatoes are fork-tender and swimming in a glossy, buttery syrup. The cinnamon and nutmeg perfume the air, and the cubes hold their shape but give easily when pressed. Stir gently to redistribute the liquid before moving on.

Mash and Top

3. 3Mash the Sweet Potatoes
   Turn off the slow cooker. Mash the sweet potatoes right in the pot with a potato masher or wooden spoon until smooth and creamy. Scrape down the sides so everything is well combined.
   Look for The mixture is thick, smooth, and free of large lumps.
   Tip For an extra-silky texture, use an electric hand mixer on low speed.
4. 4Top with Marshmallows and Pecans
   Sprinkle the mini marshmallows evenly over the mashed sweet potatoes. Scatter the candied pecans over the marshmallows.
   Look for The marshmallows and pecans cover the surface completely.
   Tip Arrange the pecans so they are evenly distributed for crunch in every bite.

The sweet potatoes have become a smooth, thick purée with a rich amber color. The marshmallows and candied pecans sit in an even layer on top, ready to melt. The mixture smells intensely sweet and buttery, and the surface is studded with crunchy pecan pieces.

Melt and Serve

5. 5Melt the Topping
   Cover the slow cooker and cook on HIGH for 15 more minutes, just until the marshmallows are puffed and golden. Watch closely so they do not burn.
   Look for The marshmallows are gooey, toasted, and beginning to brown on top.
   Tip If you prefer a deeper toast, use the broiler for 1–2 minutes after scooping.

The marshmallows are puffed, golden, and gooey, with some edges toasty and caramelized. The pecans are glossy and fragrant. The casserole is ready to scoop, with long marshmallow ribbons stretching from the spoon. Serve immediately while the topping is warm and melty.

Common mistakes

One common mistake is cutting the sweet potatoes into uneven pieces, which leads to some chunks being undercooked while others turn to mush.

Take the time to cube them uniformly. Another issue is lifting the slow cooker lid too often, which lets out heat and extends the cooking time.

Resist the urge to peek. Overcooking the marshmallows can make them deflate and turn sticky; add them only for the final 15 minutes. Finally, do not skip the stirring once halfway through, as it helps the sugar and butter distribute evenly and prevents scorching on the bottom.

How to tell it’s done

The sweet potatoes are done when they are completely tender and can be pierced easily with a fork, usually after 3 1/2 hours on HIGH. The mixture should look glossy and smell richly spiced. After mashing, the texture should be smooth and creamy with no large lumps.

The marshmallows are ready when they are puffed, softened, and lightly golden on top, after about 15 minutes. If you prefer a deeper caramelized crust, transfer the casserole to a baking dish and broil for 1 to 2 minutes, watching closely.