In the brackish marshes of the American Northeast grows Althaea officinalis, the marsh mallow plant, whose tough, tan-white roots can be boiled and used in place of egg whites in a meringue, or gelatin in homemade marshmallows.
The Ancient Egyptians once harnessed the plant’s thickening powers, mixing its sap with honey and nuts for a confection considered a candy for the gods. Later, in the 19th century, when European confectioners replaced the sap with gelatin and figured out how to mass produce it, the marshmallow came down to earth.
And lucky for us.
Watch Eric Kim Make His Sweet Potato Casserole
Credit…Matthew Young
Now, every year on Thanksgiving, the grocery-store shelves are rife with marshmallows, ready to top many a sweet potato casserole. For some, that plush-topped Thanksgiving staple is a yearly burst of saccharine sunshine. For others, it’s a repulsion of gastronomic proportions. Why top an already sweet dish with sugary candy? To understand, it might help to look at the recipe’s creation.
In 1917, the Angelus Marshmallow company hired Janet McKenzie Hill, a prolific cookbook author, food scientist and the founder of The Boston Cooking School Magazine, to create recipes that used its marshmallows. One of those inventions was the casserole we know today: mashed DayGlo-orange sweet potatoes topped with bloomed and burnished snowy marshmallows.
The sweet potato casserole’s origin is closely tied to marshmallows.Credit…Ryan Liebe for The New York Times. Food Stylist: Simon Andrews.
This year, I wanted to create a decidedly savory version that made a case for marshmallows’ rightful place on top of the casserole — and alongside the turkey, stuffing, green bean casserole and macaroni and cheese. My reasoning was not just because the original called for them, but because there’s something satisfying about a root-vegetable dish topped with a candy with origins in nature.
Here are my must-do recommendations for a dish that’s sweet, but not too sweet:
1. Bake — don’t steam — your sweet potatoes
The Idaho Potato Commission recommends not wrapping your spuds in foil, since trapped steam can cause sogginess. Instead, bake them whole, naked on a sheet pan, to reduce their moisture, and look for caramelly bubbling — that’s how you know your sweet potatoes are truly cooking. Cooking them this way results in a fluffier mash and concentrates their naturally honeyed flavor. Your final casserole will taste even more sweet potatoey.
2. Anchor the sweet with some savory
Borrowing a little flavoring trick from the chef Nick Anderer of Anton’s and Leon’s in New York, I add woodsy bay leaves and fruity black pepper, steeped in heavy cream, which give the sweet potatoes an undeniable savoriness. You could use sage or thyme or rosemary, as well, but there’s nothing like the combination of mentholly bay leaf and sugar-white marshmallows.
3. Halve the marshmallows vertically
In this recipe, the marshmallows are a necessary ingredient rather than a quirk: Halved vertically and toasted under the broiler, they create a thin, bittersweet shell that crackles and complements the potatoes, providing most of the dish’s sweetness.
4. Finally, consider a nut, any nut
The sweet potato casserole might be associated with the American South, but Ms. Hill, its creator, was based in the North. When the root-on-root delicacy arrived in the South (most likely via her recipe booklets), the too-sweet marshmallows were swapped out for nuts, often in some form of streusel or praline. A handful of pecans, which are native to North America, scattered atop the marshmallows lends necessary richness and crunch.
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