Spray a 9×13 pan or 24 muffins cups with Baker’s Joy® No Stick Spray; set aside.
In a medium bowl, whisk together the flour, baking powder and salt; set aside.
In a mixing bowl, cream together the butter, shortening, and sugar until fluffy. Scrape the sides of the bowl.
Add the egg whites, one at a time, blending after each addition and scraping the sides of the bowl as needed.
Add the extracts and blend to combine.
Stir in the sour cream. Make sure the batter is well blended and all ingredients are scraped up from the bottom of the mixing bowl.
Add the flour mixture, alternating with the half and half, beginning and ending with the flour.
Pour and spread into prepared pan or muffin tins.
Bake 30-40 minutes for a 9×13 or 17-19 minutes for cupcakes, or until a toothpick inserted in the center comes out clean.
Cool on a wire rack.
Frosting
In a saucepan over medium-low heat, combine the white chocolate with the heavy cream, stirring constantly until smooth. Remove from heat and allow to cool.
In a mixing bowl, combine the cooled white chocolate, butter, and vanilla. Beat on low to medium speed for 2-3 minutes.
Slowly add in scoops of the powdered sugar, blending in after each addition. Mix until smooth and creamy.
Spread frosting over cooled cake or pipe onto cupcakes.
