- Thoroughly dissolve the gelatin in the cold water*, in the bowl of a standing mixer, fitted with whisk attachment.
- Pour the water, corn syrup, sugar & salt into a saucepan fitted with a candy thermometer, in that order. Bring to a boil, without stirring, and then cook to 240 F. Take the pan off the burner. Leave the thermometer in the pan and shock the bottom of the pan in a bowl of ice water to stop it cooking. Allow the syrup to cool in the saucepan until the temperature is 210 F.
- Pour the syrup over the bloomed gelatin in the mixer bowl. Begin mixing at medium speed. Once the marshmallow thickens, you may increase the mixer speed to high. Whip the mixture for 5 – 10 minutes, until the marshmallow is fluffy, very thick and still warm. By the time it is done, the mixer should be laboring.
- Transfer the marshmallow to the lined, greased pan. Cover with a second piece of greased plastic wrap and press out to even the top. Allow to cure for several hours or even overnight.
- Sift powdered sugar onto a cutting board. Remove the plastic wrap and flip the marshmallow slab onto the board. Sift sugar on the top.
- Cut the marshmallows with scissors or a knife dipped in powdered sugar. Roll the cut edged in more powdered sugar. Store, in a container, indefinitely.
* Cold liquid flavorings like juice, coffee or tea can be substituted for up to 1/2 of the cold water that the gelatin blooms in. For more acidic liquids, use less or the acid will degrade the gelatin, causing the marshmallows to be too sticky. For example, to make:
- Lemon marshmallows, use 1-1/2 oz. cold lemon juice and 2-1/2 oz cold water.
- Coffee marshmallows, use 2 oz. cold coffee & 2 oz. cold water
- Pomegranate marshmallows – 1/2 oz. cold lemon juice, 1-1/2 oz. pomegranate molasses & 2 oz. cold water