With nutmeg and molasses.
The potato starch helps lower the gluten in the resulting dough; you could use cornstarch or use cake flour altogether.
Here’s a version that appeared in the November 10, 1894 edition of The Colfax (Louisiana) Chronicle:
–Sour Cream Cake.–One cupful of sugar, one and one-quarter cupfuls sour cream, one egg, one level teaspoonful soda, one-half teaspoonful salt, one-half nutmug, flour to make a soft batter.–
From the box of A.D. from Lutz, Florida, by way of Pennsylvania in the 1940s, and originating in Ohio in the 1920s.
Sour Cream Cake
Beat up 2 egg whites.
1/2 c. sugar
1 c. molasses
1 c. sour cream
1 tsp. salt
1 tsp. baking soda with
1/2 tsp. nutmeg
2 c. flour
1/2 c. potato flour.
Divide into 2 large greased floured layer tins. Bake in moderate oven 20 minutes.
When cold, put together with the following:
Yolks of 2 eggs
1 c. honey mixed with 2 Tbsp. cornstarch
1 c. milk
1 tsp. vanilla
Cook done. When cold, spread between cakes.