Add the cold water to a large mixing bowl. Sprinkle the gelatin evenly over the top and let it sit for 5–10 minutes to bloom.
In a small saucepan, combine the allulose and hot water. Heat over medium heat, stirring until fully dissolved. Continue heating until the mixture reaches 240–245°F (soft ball stage).
With the mixer running on low speed, slowly and carefully pour the hot mixture into the bloomed gelatin.
Increase speed to high and beat for 8–12 minutes, until thick, glossy, and fluffy. The mixture should hold its shape and form soft peaks.
Mix in the vanilla extract (and salt, if using).
Beat on high until the mixture form stiff peaks (almost like beaten egg whites).
Pour the mixture into a lightly greased or parchment-lined 8×8 pan, or into molds. Smooth the top quickly, as it will begin setting fast.
Allow the marshmallows to set at room temperature for several hours, or until firm. You can refrigerate to speed this up, but avoid freezing.
Cut into squares using a greased knife. If needed, lightly dust with powdered sweetener or starch to reduce stickiness. Dusting with cocoa powder will do the same and will add nice flavor as well.
Store in an airtight container and try to keep your kiddos out of them!
Notes
Use allulose for best results: It creates the softest texture and allows the marshmallows to melt and brown more like traditional ones.
Whip until thick and glossy: The mixture should hold its shape before transferring to the pan.
Work quickly: Marshmallow mixture sets fast once whipped, so pour it into the pan or molds right away.
Grease well: Lightly oil your pan, spatula, and utensils to prevent sticking.
Let fully set: Allow to set in mold or pan for several hours for best texture and clean cutting.