Gather the ingredients.
Pour the water into a saucepan and place it over high heat. Bring the water to a boil.
In a small bowl, combine the granulated sugar and cornstarch. Blend well with a whisk or spoon.
Add the granulated sugar and cornstarch mixture to the boiling water and whisk to blend thoroughly. Reduce the heat to medium and cook, stirring constantly, until the sauce is thick. Whisk the heavy cream into the thickened sauce.
Remove the thickened sauce from the heat and whisk in the butter, vanilla extract, and salt. Whisk until the butter has melted. Strain the sauce to remove any lumps.
Spoon or drizzle warm or room temperature vanilla sauce onto a cake, bread pudding, or other dish. Enjoy.