This recipe for sweet potato cake (Ipomoca batatas), perhaps descended from the many traditional recipes for sweet potato pudding, and was probably handed down for several generations. This is the kind of dessert you would find at local Southern diners in years past.
Be grateful I couldn't find a recipe for turnip cake.
Sweet Potato Cake
1 Three layer 8-inch cake
1/2 cup butter or shortening
1 cup granulated sugar
1 cup packed brown sugar
2 eggs, beaten
1 cup cooked, peeled, and mashed sweet potatoes
3 cups all-purpose flour
4 teaspoons baking powder
1/4 teaspoon baking soda
1/4 teaspoon ginger
1/4 teaspoon cinnamon
1/4 teaspoon cloves
1/2 cup milk
1 cup chopped pecans
1 teaspoon maple or vanilla flavoring
Grease and flour 3 8-inch round cake pans. Preheat oven to 350 degrees. Cream butter and sugars until light and fluffy. Beat in the eggs and sweet potatoes. In a separate bowl, mix together flour, baking powder, baking soda, and spices. Add dry ingredients alternately with milk to sweet potato mixture. (If batter seems to stiff, add 1 or 2 tablespoons of milk.) Fold in nuts and flavoring. Spoon batter into cake pans. Bake for 30 minutes. Turn out on racks. Cool and frost with Brown Sugar Icing.
Brown Sugar Icing
1 cup confectioners' sugar
3/4 cup (packed) dark brown sugar
1/2 cup whipping cream
1/4 cup (1/2 stick) unsalted butter
1/4 teaspoon vanilla flavoring
Sift confectioners' sugar into medium bowl. In a medium saucepan over medium-low heat, stir brown sugar, whipping cream, and butter until butter melts and sugar dissolves. Increase heat to medium-high and bring to a boil. Boil 3 minutes, stirring occasionally. Remove from heat and stir in vanilla. Pour brown sugar mixture over confections' sugar, whisking. Whisk until smooth and lightened in color, about 1 minute. Cook icing until lukewarm and icing falls in heavy ribbon from spoon, whisking often, about 15 minutes. Stack layers, thinly icing between. Spoon icing thickly over top, allowing it to drip down sides of cake. Serve after icing is firm, at least 1 hour.
I like to let the cake rest overnight.