Preheat oven to 350 degrees and gather all your ingredients.
Prepare your mashed potatoes and allow them to cool before using them in the recipe.
In mixing bowl, cream butter and sugar together until light and fluffy.
Add in potatoes, eggs and vanilla
In large bowl, combine the remaining dry ingredients.
Add ½ dry ingredients, then half the milk.
Repeat.
Beat on high for 30-45 seconds, until the batter is well mixed.
Spray springform pan with cooking spray. You may also want to use a liner for the pan, to prevent the bottom from sticking.
Pour batter into 9” springform pan.
Bake cake for 45-50 minutes, or until knife or toothpick inserted in the center comes out clean.
Let the cake cool for at least 10 minutes, then use a butter knife around the edge of the cake to loosen it from the sides.
Release pan and let the cake completely cool.
Sprinkle with powdered sugar.
Serve