You'll need a stand mixer to whip in as much of that wonderful, life-sustaining nitrogen-oxygen mashup into your marshmallows as you can because the air we breathe is one component that isn't listed.
But first, lightly dust the bottom of an 8 x 8 pan or glass dish with powdered sugar, which will serve as your non-stick coating, and then put it aside.
Next, mix two seven-gram packages of unflavoured gelatin and half a cup of boiling water in a medium bowl and set aside. Boil half a cup of water and half a cup of granulated sugar in a shallow saucepan to make a simple syrup.
Let the mixture approach 240 F. Mix the hot simple syrup and reserved gelatin liquid in the mixer's bowl on high until meringue-like peaks form. Unset marshmallow mix will be comparable to jarred marshmallow fluff when ready to distribute, but fluffier.
Finally, use a silicone spatula to transfer the sticky mixture to the powdered sugar-dusted pan or dish. After topping, let set for two hours before cutting into cubes. An airtight container can keep them for three weeks.