Adapted from: http://joepastry.com/2008/homemade_marshmallows/
4 tablespoons water
3/4 cup isomalt or sorbitol (you can sub this for erythritol, but the marshmallows will only last a day or two before the erythritol crystalizes and the marshmallows turn grainy)
1/4 cup erythritol or xylitol
2 egg whites (optional)
1.5 tablespoons gelatin
2 tablespoons cold water
1/4 teaspoon pure vanilla extract (or other flavoring)
Sprinkle the gelatin over the 2 tablespoons cold water and let dissolve.
Combine the 4 tablespoons of water and all the isomalt and erythritol in a saucepan fitted with a candy thermometer. Bring to a boil and boil to “soft-ball” stage, or about 110 degrees C.
Meanwhile, whip the egg whites until soft peaks form (if using).
When the syrup reaches soft-ball stage, remove it from the heat, add the gelatin, and mix. Pour the syrup slowly into the whipped egg whites while beating. Add the vanilla and continue whipping until stiff and mostly cooled. Transfer to a pastry bag with a large plain tip. Pipe directly onto powdered erythritol (or xylitol)-covered non-stick mat or molds and let set until ready to use, at least 1 hour or overnight.
Tastes great on top of a low-carb hot cocoa or hot chocolate.