Listen, I know that casseroles are supposed to be just “throw it together and bake” types of dishes, but sweet potato casserole is typically reserved for special holidays like Thanksgiving and Christmas, and if I’m going to make anything on those days, I’m going to make it right. That means no dried out turkey, no soggy lasagna, no gluey mashed potatoes, and no less-than-perfect sweet potato casserole. Luckily, this recipe for the Ultimate Sweet Potato Casserole is here to elevate your holiday cheer and consumption this season. Be warned, once you make this version, you’ll be on sweet potato casserole duty for the next decade, at least.
What’s the big issue with most sweet potato casserole recipes? For me, it’s the fact that it’s either loaded up with ridiculous amounts of sugar and butter which takes away from the sweet potato itself, or it’s not nearly sweet enough and texturally undesirable. If you’ve ever eaten a casserole made from boiled sweet potatoes, then you probably know what I’m talking about. Boiling sweet potatoes leaves the starches intact, making them fluffier when mashed and and far less flavorful, rather than creamy and sweet. However, roasting the potatoes over a relatively low heat for a longer time breaks down those starches and converts them to sugars, making a naturally sweeter sweet potato that can be mashed much easier to achieve a smooth consistency.
I use J. Kenji Lopez-Alt’s method of wrapping the sweet potatoes in foil and then roasting in a 300 degree oven until soft and mashable in order to create the tastiest base possible for my sweet potato casserole. Bonus: the skins slide right off after roasting, so you don’t need to bother with a vegetable peeler!
That’s not to say that the Ultimate Sweet Potato Casserole is completely devoid of sugar or butter, though. No, I just use much less. Once I mash the sweet potato, I add in brown sugar, maple syrup, butter, evaporated milk, vanilla extract, a tiny bit of salt, and 3 egg yolks. The egg yolks give a velvetier, more custard-like consistency to the sweet potato casserole than you’d find from using whole eggs, and I’m able to use the reserved egg whites to make the marshmallow meringue topping. That’s efficiency, right there!
After smoothing the sweet potato mixture into my baking dish, I prepare the pecan streusel topping. To make a good streusel, cold butter needs to be cut into brown sugar and flour until small crumbs are formed, but that can get pretty tedious. I use my food processor instead to cut down on time, which also makes it less likely that the butter will soften and smush the crumbs together. Once I’ve got my streusel prepared, I spoon it on top of the sweet potato casserole in an X shape, and then fill in the empty area with 4 smaller triangles as shown above. You can also do different designs, like diagonal lines or simply cover the entire dish with the streusel if you prefer.
While I bake the streusel-topped casserole, I prepare the marshmallow meringue topping. I first beat the egg whites with cream of tartar until stiff peaks form, and then I add in sugar, vanilla extract, and marshmallow fluff. That’s all it takes. This mixture can either be spooned on top of the baked casserole or piped on to fill the empty spots between the streusel. Since we’re not covering the entire dish with marshmallows, we can still count it as a side dish if we want, right? I always feel like using too many marshmallows brings sweet potato casserole too far in to dessert territory to deny.
Once I’ve filled in all of the empty spots (and added a dot in the bottom-center of each small streusel triangle), I pop the casserole back in the oven until the marshmallow meringue begins to brown slightly on top. The final product is a gorgeously patterned sweet potato casserole that tastes even better than it looks.
It’s a good thing that the maple and brown sugar in the casserole make it so fragrant and appealing, or I might feel too guilty about messing up that design to scoop some out to serve.
There is a small comfort in the fact that it’s commemorated forever on this blog in the form of that photo above, at least.
Serve this sweet potato casserole at your next holiday dinner and let me know if you think it deserves the title of the “Ultimate Sweet Potato Casserole”! Don’t forget to take a photo and tag it on Instagram or Twitter with #hostthetoast so you can show off that pecan streusel and marshmallow meringue masterpiece!
- 3 sweet potatoes (about 2 lbs)
- 2 tablespoons brown sugar
- ¼ cup maple syrup
- 3 egg yolks (whites reserved)
- ½ teaspoon salt
- 4 tablespoons unsalted butter, softened
- ½ cup evaporated milk
- 1 teaspoon vanilla extract
- ¼ cup brown sugar
- 3 tablespoons flour
- 3 tablespoons unsalted butter, cold
- ⅓ cup chopped pecans
- 3 egg whites
- ¼ teaspoon cream of tartar
- ¾ cup granulated sugar
- 1 teaspoon vanilla extract
- ¾ cup marshmallow fluff
- Tear off 2 sheets of aluminum foil, about 2’ long each. Place one sheet on top of the other, and then place the sweet potatoes on top. Wrap up the sweet potatoes with the foil, crimping the seams to seal so that steam doesn’t escape. Place the foil packet on a rimmed baking sheet and place in the oven. Set the oven to 300 degrees F and roast for 2 hours, or until the potatoes are soft enough to mash.
- Remove the sweet potatoes from the oven, open the packet, and let them sit until they’re cool enough to handle.
- Peel the sweet potatoes and discard the skins. Place the potato flesh in a large bowl and mash with a fork. Add in the remaining casserole base ingredients and mix with a hand blender until well-combined and smooth.
- Preheat the oven to 350 degrees F. Spray a square baking dish with nonstick spray and spoon the sweet potato mixture into the dish. Smooth it with the back of a spoon so that the sweet potato is all in an even layer. Set aside.
- Place all of the pecan streusel ingredients except for the pecans in the bowl of a food processor and pulse until the mixture forms small crumbs. Add in the pecans and pulse again to combine evenly, making sure not to over process. Spoon the streusel over the casserole in an X shape, and then fill the open areas with small triangles, leaving at least an inch of open space between the edges, as shown in the pictures above. Bake for 30 minutes.
- As the casserole bakes, prepare the marshmallow meringue. Beat the egg whites with the cream of tartar in a large bowl until stiff peaks form. Slowly add in the sugar while mixing until fully combined. Add in the marshmallow fluff and vanilla extract and beat again until sticky and still able to hold peaks.
- When the casserole is ready, remove it from the oven and pipe or spoon marshmallow meringue into the empty areas. If you make a mistake, just scoop the marhsmallow off with a spoon and pipe again-- you will have extra meringue so you can fix any little errors. Once you have the empty area filled in, add in an extra drop of marshmallow meringue in the bottom-center of each small streusel triangle as shown in the pictures above.
- Return to the oven and bake until the meringue begins to brown, about 15-20 minutes. Serve warm.
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