Preparation / Directions:
Butter a 9x13-inch baking pan. Combine the powdered sugar and cornstarch in a small bowl. Use a third of the mixture to coat the pan and reserve the rest. Shake the powder combination around in the pan so that it adheres to the sides of the pan as well as the bottom.
Combine the sugar, gelatin and salt in a saucepan. Stir in the cold water and allow to rest for 5 minutes until gelatin softens. Place over low heat and, stirring constantly, heat until the sugar has dissolved. (The mixture should not boil. ) When the sugar is dissolved, remove from heat and allow to cool to room temperature. Stir in the vanilla extract. Pour the mixture into a large bowl and, using an electric mixer, beat at high speed until it is thickened and will stand in soft peaks (about 10 to 15 minutes of beating).
Pour the mixture into the pan, spreading to make it smooth and even. Dust the top with the second one-third of the powdered sugar-cornstarch mixture. Loosely cover with foil and let it stand at room temperature undisturbed for at least two hours or overnight. When the block of candy has set up, remove it from the pan and cut into 1-inch squares or whatever other design you choose. (Dip the knife or cutter into cold water to keep from sticking). Sprinkle with remaining powdered sugar-cornstarch. Store the marshmallows at room temperature in an air-tight container and use within 2 months.