Marshmallows were very trendy at the turn of the 20th century. Formerly an expensive, handmade treat, machines had been invented to automate the process. Using marshmallows in one’s kitchen was considered very modern, as well as labor saving: housewives were encouraged to substitute them for meringue and whipped cream, two very laborious toppings.
The first recipe to top candied sweet potatoes with marshmallows allegedly comes from a 1917 Angelus Marshmallow recipe booklet, but I haven’t been able to lay my hands on a copy to verify that claim. The earliest recipe I’ve seen comes from a 1918 trade journal called Sweet Potatoes and Yams. It’s filled with growing and storage tips for tubers.
3 pounds sweet potatoes (about 3 large), peeled and cubed
1/2 cup sugar
1/2 cup 2% milk
2 large eggs, lightly beaten
1/4 cup butter
1 teaspoon vanilla extract
3/4 cup all-purpose flour
3/4 cup packed brown sugar
3/4 cup old-fashioned oats
1/8 teaspoon salt
1/3 cup cold butter, cubed
2 cups miniature marshmallows
Preheat oven to 350°. Place sweet potatoes in a 6-qt. stockpot; add water to cover. Bring to a boil. Reduce heat; cook, uncovered, 10-12 minutes or until tender. Meanwhile, make topping by combining flour, brown sugar, oats and salt; cut in butter until crumbly.
Drain potatoes; return to pan. Beat until mashed. Add sugar, milk, eggs, butter and vanilla; beat until combined. Transfer to a broiler-safe 13x9-in. baking dish. Sprinkle topping over potato mixture.
Bake, uncovered, until topping is golden brown, about 45 minutes. Sprinkle with marshmallows. If desired, broil 4-5 inches from heat, 30-45 seconds or until marshmallows are puffed and golden.