Place an empty metal bowl into freezer for 30 minutes.

In a saucepan on the stove combine powdered sugar and cornstarch with a whisk. Stir in 1/2 cup cream until smooth. Cook over medium heat stirring constantly so it doesn’t scorch. Stir until mixture thickens not quite to a boil. Remove the mixture from heat, transfer to a a non-chilled bowl and stir occasionally until room temp.

Remove the chilled bowl from freezer and pour in 2.5 cups of cream and 1 teaspoon vanilla extract and whip with an electric mixer until it is soft set. When the hot sugar mixture is completely cooled begin adding it to the chilled bowl a little at a time. Beat this mixture just until sift peaks are formed. Frost the cakes immediately. Store the cakes in the refrigerator until ready to serve and remove the cakes from refrigerator 15 minutes before serving.