Water, agave syrup (or corn syrup), and sugar should be combined in a pot. Stir continuously until the water and sugar are well combined.

If you're not using agave or corn syrup, put the sugar in the pan and then pour water all the way to the edge. To allow the water to spread and saturate the sugar, use your finger to create a wall-to-wall "X" in the sugar.

Boil the sugar syrup until it boils over medium-high heat. To distribute heat evenly, gently swirl the pan.

Put a lid on the saucepan and adjust the heat to medium-low. Give the syrup two minutes to cook. It is not the time to raise the lid.

Take off the cover and examine after two minutes.

Remove the lid after two minutes and inspect the side of the saucepan for any sugar crystals. If there are crystals, continue cooking the mixture with the lid off for an additional minute to let the condensation dissolve the crystals into the syrup.

Set the sugar thermometer's temperature between 242 and 245 degrees Fahrenheit. Clip it to the side of the saucepan. Until the sugar syrup reaches this temperature, let it cook. Please check the sugar stage every five minutes until it reaches the firm-ball stage if you don't have a sugar thermometer (please read the recipe notes in the post to learn how to do this).

Make the gelatin while the sugar syrup is heating up. 12 cup of water should be added to the mixing bowl.

Water and gelatin are combined to make the gelatin wet. Put aside while the sugar syrup is heating to for the gelatin to bloom (at least 10 minutes). Using the whisk attachment on your mixer, place the bowl inside.

Remove the sugar syrup from the heat when it reaches the proper stage, and wait for the bubbles to stop.

Pour the sugar syrup into the gelatin along the bowl's edge while the mixer is set to medium-low speed (this is to prevent the gelatin from being scorched by the hot sugar syrup). Increase the speed to medium-high after adding the salt.

The marshmallow base should double in size and be smooth, white, and fluffy after 3 to 5 minutes of medium-high mixing.

Let the marshmallow to continue to volumize by mixing for an additional 3 to 5 minutes at high speed (upto 3 times). Because doing so will result in harsh marshmallows, never combine a cooled marshmallow base. (You can whisk the marshmallow on high for 5 to 6 minutes to cut the time in half; just make sure the foundation is fluffy, white, and up to three times as much as the original volume.)

Prepare your pan and cooking implements while the marshmallow foundation is being whisked. You can line an 8 x 8-inch pan with parchment paper and then rub it with shortening or butter.

Add the vanilla to the marshmallow foundation and whisk for an additional minute on high speed to incorporate the vanilla (and egg whites, if using) (and egg whites).

Using a flexible scraper or cake spatula that has been lightly greased, scrape the marshmallow base into the prepared pan.

With the lubricated spatula, distribute the marshmallow evenly in the pan.

Sprinkle confectioners' sugar on top of the marshmallow and let it sit for at least six hours to solidify.

Onto a work surface that has been sprinkled with dusting powder, spread out the set marshmallow.

Use a knife or pair of scissors that have been lubricated to cut the marshmallows. Place the marshmallow in the dusting powder, then seal the container tightly.