Homemade marshmallows are so much better than prepackaged, store-bought ones. They are easy to make; you just need a little time. They will need at least 4 hours to cool and set up.
Stir gelatin and ½ cup water (113 grams) together in the bowl of a stand mixer (or another large bowl if using a handheld electric mixer).
In a heavy medium saucepan, combine sugar, corn syrup, and ½ cup water (113 grams). Heat over medium to medium-high heat, stirring to combine. Bring mixture to a boil.
When it boils, place a candy thermometer in it, and heat until it reaches 240F. (I usually do not stir the syrup.) This step can take as little as 10 minutes, or as long as 30, depending on how hot you have your burner.
Turn stand mixer on low, and break up the softened and bloomed gelatin using the whisk attachment; otherwise, it may not dissolve. With the mixer still running, slowly pour in the syrup.
Turn the mixer up to high and whisk for 7 minutes. The mixture will grow in volume and turn white and frothy.
While the mixer runs, prepare your pan. Spray the bottom and sides of a 9x13-inch pan (I prefer glass for easy clean-up) with cooking spray and dust completely with powdered sugar. Set aside.
After the mixture has been whisked for 7 minutes, it will be fluffy and white. Drizzle in the vanilla, very slowly, along the side of the bowl. (If you pour it in directly the marshmallow or too fast, marshmallow will spatter out.) Mix for 30 seconds or a minute, until completely incorporated. If desired, add in other mix-ins now and mix for another 30 seconds.
Use a greased spatula to spread the marshmallows into the prepared pan. Smooth out the top as best as possible. Dust with powdered sugar. Cool for a few hours, then cover and let set overnight, or at least 4 hours.
Turn out onto a cutting surface. (I turn mine out an oversized cutting board.) You may need to use a spatula or knife to loosen the edges of the mallows from the side of the pan, but I've been able to pull mine out easily with my hands most recently.
Cut into cubes using a pizza cutter or bench scraper. Coat with additional powdered sugar, particularly along the cut edges.
Store between layers of waxed or parchment paper in an airtight container at room temperature. Kept away from heat at humidity, marshmallows will last about a month.
A candy thermometer is essential for this recipe.
I've always made homemade marshmallows using a stand mixer. You should be able to use an electric handheld mixer, but you will have to mix for longer, and they may not be as fluffy.
You must bloom the gelatin for this recipe to work. You cannot substitute anything else for the gelatin.
For softer, creamier marshmallows, you can try to cut the gelatin back to 2 packets. However, I have not tried this.
Try dusting with powdered sugar blended with cinnamon or cocoa powder for a variation. You can add peppermint or other extracts, or crushed candy canes if desired.
Originally adapted from King Arthur Baking