I have so often used potato starch as a thickener for sauces, soups, and stews but for adding it to my flour for baking, this is my first. Potato starch is not potato flour. Potato flour is dehydrated potatoes ground into powder and is much heavier and denser. Potato starch is the result of an extraction process removing the starch only from the potato. Think of the white foam that floats to the top when you boil potatoes, that's potato starch. Potato starch has no gluten. It is used in recipes for those who are gluten intolerant.
Potato starch tolerates higher temperatures than cornstarch when used as a thickener, but for baked good, it's a natural way to add moistness, therefore a fine crumb and soft textured cake..
You can find potato starch on the baking aisle at most of your local supermarket and and health-food stores. I get mine from the asian stores here, they are very much cheaper and a variety of brands to choose from.
This Yellow Butter Cake recipe has 1/3 of the wheat flour replaced with potato starch which is 1/2 cup/2 ozs by weight. This replacement made the crumb fine, soft and moist, in fact, the cake tasted better the next day.
6 3/4 oz/1 1/2 cups all-purpose flour
2 ozs/1/2 cup potato starch
1 1/2 tsp baking powder
1 tsp salt
1 cup fine granulated sugar(add more if you like a sweeter cake - max another 3/4 cups)
6 ozs/10 tbsp butter - softened
3 large eggs
3/4 cup whole milk
1/4 cup half-and-half
2 tbsp bourbon (optional)
1 tbsp vanilla extract
Preheat oven to 350 f
Line bottoms of 2(9 inch) cake pans with parchment paper, grease cake pans and parchment paper.
Weigh or lightly spoon flour into dry measuring cups, level with a knife.
Weigh or lightly spoon potato starch into dry measuring cups, level with a knife.
Combine flour, potato starch, baking powder and salt, stirring well with a whisk.
Place 1 cup sugar and 6 ozs butter in the stand mixer bowl, beat at medium speed until light and fluffy. Scrape down sides of bowl, now and then.
Add eggs, 1 at a time, beating well after each addition.
Combine milk, half-and-half., vanilla extract and bourbon(if using)
Turn speed to the lowest , add flour mixture and milk mixture alternately to butter mixture, beginning and ending with flour mixture.
Beat just until combined.
Divide batter evenly between prepared pans.
Bake at 350 f for 28 minutes or until a wooden pick inserted in center of cake comes out clean.
Cool in pans 25 minutes on wire rack; remove from pans.
Cool completely on wire racks.