You will need:
3/4 cup powdered sugar
1/2 cup cornstarch or potato starch
Cooking spray, for coating the baking pan
4 1/2 teaspoons unflavored powdered gelatin (about 2 [1/4-ounce] packets) 3/4 cup cold water
3/4 cup granulated sugar
1/2 cup light corn syrup
1/8 teaspoon fine salt
2 teaspoons pure vanilla extract
Besides the ingredients you will also need an 8x8 pan and an electric mixer with a whisk attachment
Start by mixing the powdered sugar and corn starch together. This will be a powder coating to prevent the marshmallows from sticking together.
Prepare the 8x8 pan by lightly spraying it with cooking spray. (to achieve a lighter coating, refrain from letting your 4-year-old from doing this step) Add a couple of spoonfuls of the powdered sugar/corn starch mixture and shake the pan until it has a nice even coating. Now add the sugar, 1/4 cup of the corn syrup, remaining 1/4 cup water, and salt in a medium saucepan. Bring it to a boil, stirring until it hits 240 degrees. While waiting for the right temperature, microwave the gelatin for 30 seconds. Add the rest of the corn syrup and the gelatin to you mixer and start it on low.
Once the mixture on the stove reaches 240 degrees add it to the mixer also. Turn the speed up to medium and let it whip for 5 min. After 5 min increase the speed to medium high for another 5 minutes.
Your mixture should be looking mighty fluffy at this point. Add your vanilla (and/or any other flavors you want) and increase the speed to the highest setting for a few minutes.
Dust the top with more of the powdered sugar/corn starch mixture. (put the rest of the powder mixture on the side to use after the marshmallows set up.) Put the pan in a cool, dry place for at least 4 hours (overnight works best)
When they are all set up, flip the pan over onto a cutting board. Use a pizza cutter dusted with your powder mixture to cut out bite-sized marshmallows.
After cutting, toss each piece in the powder mixture to prevent them from sticking together and store in an airtight container. They will keep for several weeks (although they probably won;t be around for that long)