1 Mix the gelatin with the water, then set it aside. Pour ½ cup (120 milliliters) of cold water into a small bowl. Stir in 2 envelopes of unflavored gelatin. Set the bowl aside for 10 minutes so that the gelatin can "bloom." During this time, you can prepare the rest of the ingredients.

2 Prepare a 9 by 9-inch (22.86 by 22.86-centimeter) square baking pan. Lightly coat the bottom and sides of a 9 by 9-inch (22.86 by 22.86-centimeter) baking pan with cooking oil. Generously dust it with powdered sugar or cornstarch.

3 Dissolve the granulated sugar with the rest of the water. Pour the remaining ½ cup (120 milliliters) of water into a saucepan. Stir in the granulated sugar (not the powdered sugar). Clip a candy-making thermometer to the saucepan so that it's ready for the next step.

4 Add the gelatin, then bring the sugar water to 240°F (115°C). Stir the gelatin water into the sugar water. Bring the solution to a boil over medium heat. Let it cook until it reaches 240°F (115°C). Do not stir during this time.

5 Remove the saucepan from heat and add in the salt and vanilla extract. Once the sugar water reaches 240°F (115°C), take the saucepan off the stove and set it down onto a heat-safe surface. Stir in the salt and vanilla extract. If you don't like vanilla, you can leave it out or replace it with a different extract.

6 Beat the sugar water in an electric mixer until it doubles in volume. Pour the sugar water into the bowl of an electric mixer fitted with whisks. Beat it on a low-speed setting for 2 minutes, then beat it on high for 10 to 15 minutes. It's ready when it turns soft and twice its size.

7 Transfer the mixture to the prepared pan. Use a rubber spatula to help spread the mixture across the bottom of the pan, from corner-to-corner. If the marshmallow mixture is sticking to the spatula, lightly coat it with cooking oil first.

8 Allow the marshmallow mixture to set for 3 hours. Leave it uncovered someplace where it won't get disturbed. Once it finishes cooling, dust it with ½ cup (65 grams) of powdered sugar.

9 Cut the marshmallow mixture into 1-inch (2.54-centimeter) squares. Turn the marshmallow slab onto a cutting board. Use a pizza cutter or a sharp knife to cut it into 1-inch (2.54-centimeter) squares. If the marshmallows are too sticky, coat the blade with some cooking oil.