Keep blending for a very long time to get a velvety consistency. This is one of those recipes that really makes use of the power of a high-speed blender. If you feel that the blades are just spinning but aren’t actually moving all of the icing around, turn the blender off and make an air pocket down the side of the blender with a spatula to expose the blades. Remove the spatula, replace the lid, and start blending slowly again.