These fluffy, bouncy marshmallows mimic the technique of meringue, but stay distinctly soft and marshmallow-y. They are by far the easiest way to make vegetarian marshmallows, and you won't have to go searching for any crazy ingredients to make them happen!
Position a rack in the center of the oven and preheat to 200°F.
Add the egg whites to the bowl of a stand mixer. Using the whisk attachment, whip the egg whites on medium-high for 3-4 minutes or until you have soft peaks.
Reduce the mixer to medium and add in the 1/2 cup (100g) of sugar in three increments, mixing for 2-3 minutes in between each addition.
Once the sugar is combined and the egg whites are beginning to look glossy and stiff, add in the 1/4 cup (37g) cornstarch. Mix on medium-high speed until the cornstarch is just combined.
Pour the 1/3 cup and 1 tablespoon (100g) of corn syrup into a small pot. Bring this to a simmer, let it get to between 230°F-240°F. Once it is in that range, stream it down the side of the mixing bowl into the mixer while the mixer is on medium-high speed.
When the corn syrup is fully incorporated, stop the mixer.
Line a half sheet pan with parchment paper. Use a 3 tablespoon cookie scoop to scoop the marshmallows onto the sheet pan. It will make around 20.
Bake these in the oven for 30-35 minutes at 200°F. They are done when the tops are dry and they are spongy to the touch. Let them cool completely before using (otherwise they might feel a bit too moist in the center).
To store these, dust both the tops and bottoms with cornstarch so that the entire marshmallow is coated in a thin layer. Store these at room temperature in an airtight container for up to 7 days.
Notes
Want to infuse these with other flavors? Here are a few to try!For chocolate marshmallows: Add 2 tablespoons Dutch-processed cocoa along with the cornstarch. For "tiramisu" marshmallows: Add 1 tablespoon of rum in with the sugar, then add 1/4 teaspoon of espresso grounds with the cornstarch. For "chai" marshmallows: Blend up 2 teaspoons of a masala chai spice blend with spice grinder until you have a powder. Add this in with the cornstarch. For "peppermint" marshmallows: Add 1/2 teaspoon peppermint extract in after adding the cornstarch.