How-to Make Homemade Marshmallows
With mixer on low speed, stream hot cooked syrup slowly into bowl, combining it gradually with the softened gelatin.
Beat on high speed until mixture is thick and volume has doubled—about 15 minutes—before adding vanilla.
Spread onto foil-lined pan. Using foil, lift marshmallows out of pan and cut into 1-inch squares with a knife or pizza cutter coated with cooking spray.