Pour 1/3 cup of cold water into a large bowl. Sprinkle the unflavored gelatin on top of the water and allow it to sit – undisturbed – for five minutes.
Combine the sugar, corn syrup, salt and 1/3 cup water in a saucepan and bring to a boil. Continue to boil the mixture – stirring occasionally – until the mixture reaches the soft-ball stage which is 238 degrees F.
Begin mixing the gelatin and water together using a mixer on the lowest speed. Slowly add the hot syrup to the gelatin mixture while continuing to mix.
Once the two liquids are combined, gradually increase the speed of the mixer until it is on high speed.
Once the liquids look thick, white and are triple the volume you began with (this process takes about 12 minutes), add the vanilla and beat for 30 seconds.
Quickly pour the marshmallow mixture into greased molds or spread it out on a greased cookie sheet to dry.
Once the marshmallow mixture is cool, unmold it or use greased cookie cutters to cut it into the shapes you desire.