Makes about 90 1-inch cubes

Ingredients

1 cup powdered sugar
2 tablespoons powdered, unflavored gelatin (about three and a half envelopes)
2 cups granulated sugar
1 cup cold water
1/2 cup light corn syrup
1/4 teaspoon salt
2 egg whites
1 tablespoon vanilla extract
Flavorless cooking oil

Directions

Lightly oil a rectangular baking pan and dust with confectioner's sugar. Set aside.

In the bowl of an electric stand mixer, sprinkle gelatin powder over 1/2 cup of cold water, and leave to stand until softened, about 5 minutes.

In a heavy saucepan, add sugar, syrup, the remaining 1/2 cup water and salt over a low heat, stirring until sugar is dissolved. Stop stirring and turn the heat up until the mixture boils and reaches the candy-making stage at 240 degrees F with a candy thermometer. Tip: If you don't have a candy thermometer, test it by dropping a small amount into a cup of cold water. If it turns solid, then it's ready.

Remove from the heat and pour over the gelatin mixture, stirring until the gelatin in dissolved.
Turn the mixer on high speed and beat until fluffy, white and tripled in volume (for about 6 minutes).

In another bowl, with clean beaters, beat egg whites until stiff peaks form. Fold whites and vanilla into sugar mixture until just combined.

Pour out onto dusted baking pan, and dust with more confectioners’ sugar. Chill, uncovered in the refrigerator until firm. Remove marshmallow slab from pan and cut using an oiled kitchen knife.

Keep in a airtight container at cool room temperature for up to one week.