Vanilla sauce is made by adding a sugar and cornstarch mixture to boiling water and cooking it until it is thickened. Once the cornstarch and sugar syrup is thickened, it is removed from heat and butter, vanilla extract and a pinch of salt are added to it.
To make vanilla sauce, heat 1 cup of water to boiling over medium heat. While the water is heating, combine 1/2 cup sugar with 1 tablespoon of cornstarch. Once the water reaches a boil, add the water and cornstarch mixture, and reduce the heat. Let the mixture simmer until it thickens into a syrup. Remove the syrup from the heat, and add 2 tablespoons of butter and 2 teaspoons of vanilla extract along with a pinch of salt to taste.
Vanilla sauce is commonly spooned over bread puddings or cakes, though it can be used to top almost any dessert. Some variations also add bourbon or other flavors. Vanilla is the most common ingredient in dessert recipes. It is also second only to saffron in value when it comes to spices. Pure vanilla is derived from an orchid plant. Because it is so expensive, most vanillas used in cooking and baking are extracts or completely synthetic versions of the spice.