Prepare a 9x13 casserole dish by either greasing it (very well) or lining it with parchment paper.
Combine 1/2 cup of water with 4 Tbsp of gelatin in your mixing bowl or stand mixer and set aside.
Combine the other 1/2 cup of water and sugar in a saucepan and heat until it starts to boil. Note: If you are using granulated sugar, be sure the sugar dissolves before removing from the heat.
With your stand mixer, start whipping the gelatin, then slowly pour in the sugar/water mixture while whipping.
Increase the speed of your mixer and whip for around 10 minutes. You're looking for the ingredients to become very fluffy and eventually develop a slight tackiness (like a marshmallow texture, but still pourable).
Pour into the prepared greased or lined pan
Let it rest at room temperature for about 4 hours to firm up.
Once the marshmallow mixture has reached your desired texture, wet a large knife and cut into squares. To do this, you can either lift the parchment paper out, place on acutting board and cut. OR if you didn't use parchment paper, you should sprinkle powedered sugar onto your cutting surface so that it doesn't stick.
Served with hot chocolate or use as desired.
Store leftover marshmallows in an airtight container.
Notes
If the marshmallows are way too sticky to cut, try coating them with powdered sugar.