When measuring flour, we spoon it into a dry measuring cup and level off the excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.) If you can't find plain peanut butter ice cream, try this quick "homemade" version: Stir 1/2 cup smooth peanut butter into 2 1/2 cups softened vanilla ice cream. Just make sure to refreeze your "homemade" peanut butter ice cream so that it's not too soft when you are assembling your cake.