1. In a heavy-bottomed saucepan, combine the granulated sugar, corn syrup, 1/3 cup water, and salt. Clip a candy thermometer to the side of the pan, making sure the bulb doesn’t touch the bottom (this gives false readings).
2. While the sugar mixture is heating, sprinkle the gelatin over 1/3 cup cold water in the bowl of your stand mixer. Let it sit and bloom—it’ll look weird and lumpy, but that’s exactly right.
3. Cook the sugar mixture over medium heat, stirring occasionally at first, then stop stirring once it comes to a boil. Let it bubble away until it reaches exactly 240°F on your candy thermometer—this is crucial, so don’t guess.
4. Once the syrup hits 240°F, immediately remove it from heat. With the stand mixer running on low speed (use the whisk attachment), slowly and carefully pour the hot sugar syrup into the bloomed gelatin. Be very careful—this stuff is extremely hot and will burn you badly if it splashes.
5. Once all the syrup is added, increase the mixer speed to high and let it beat for 10-15 minutes. You’ll see it transform from thin and syrupy to thick, white, glossy, and tripled in volume—like shaving cream. Add the vanilla extract somewhere in the middle of this process.
6. While the marshmallow is whipping, mix the cornstarch and powdered sugar together in a small bowl. Lightly grease a 9×13 inch baking dish (or 8×8 for thicker marshmallows), then generously dust it with the cornstarch-sugar mixture, coating the bottom and sides.
7. Once the marshmallow mixture is thick, glossy, and holds stiff peaks, pour it into your prepared pan. Use a greased spatula to smooth the top—it’ll be sticky and stretchy.
8. Dust the top generously with more cornstarch-sugar mixture, then let it sit uncovered at room temperature for at least 4 hours or overnight until completely set and firm to the touch. Don’t refrigerate—just let it sit out.
9. Once fully set, turn the entire slab out onto a cutting board that’s been dusted with more cornstarch-sugar mixture. Cut into squares with a sharp knife (dip the knife in the coating mixture between cuts), or use greased cookie cutters for fun shapes.
10. Toss each cut marshmallow in the cornstarch-sugar mixture to coat all sides and prevent sticking. Shake off any excess in a fine-mesh strainer if you want them less dusty.
11. Store in an airtight container at room temperature, layered between parchment paper if stacking. They’ll keep for about 2 weeks, though they never last that long around here.

Nutrition Information (Per Marshmallow, 64 servings):

• Calories: 35
• Carbohydrates: 9g
• Protein: 0.5g
• Fat: 0g
• Fiber: 0g
• Sodium: 10mg
• Sugar: 7g

These are basically pure sugar and gelatin, so they’re a treat—not a health food. But they’re lower in calories than you might think, and way better quality than store-bought.

Notes:

• Seriously, don’t skip the candy thermometer—guessing the temperature doesn’t work reliably
• Beat the mixture for the full 10-15 minutes; stopping early gives you dense marshmallows
• Keep everything well-coated in that cornstarch-sugar mixture to prevent sticking
• Humid weather can make setting take longer and can make them stickier overall
• Hot sugar syrup is dangerous—be careful when pouring and keep kids away from the stove

Storage Tips:

• Store in an airtight container at room temperature for up to 2 weeks
• Layer between sheets of parchment paper if stacking to prevent sticking
• Don’t refrigerate—moisture will make them weird, sticky, and unpleasant
• They’ll gradually firm up over time but will still be delicious
• Keep them well-coated in cornstarch-sugar mixture to maintain texture

Serving Suggestions:

• Hot Chocolate Toppers: Float them in hot cocoa for the ultimate winter treat—they melt into creamy deliciousness
• S’mores Station: Toast them over a fire or under the broiler for classic s’mores with graham crackers and chocolate
• Rice Crispy Treats: Use them fresh for the most incredible rice crispy treats you’ve ever tasted
• Gift Giving: Package in clear bags tied with ribbon for adorable homemade gifts that people actually want

Mix It Up (Recipe Variations):

• Peppermint Marshmallows: Add 1/2 teaspoon peppermint extract along with the vanilla for holiday hot chocolate
• Chocolate Swirl Marshmallows: Drizzle melted dark chocolate over the marshmallow slab before it sets, then swirl with a knife
• Strawberry Marshmallows: Mix freeze-dried strawberry powder into the cornstarch coating for natural color and fruity flavor
• Toasted Coconut Marshmallows: Roll the finished marshmallows in toasted coconut instead of cornstarch-sugar mixture

What Makes This Recipe Special:

This classic confection showcases the fascinating science of sugar chemistry and gelatin stabilization, where hot sugar syrup is whipped with hydrated gelatin to create a stable foam structure filled with thousands of tiny air bubbles. The technique of heating sugar to the soft-ball stage (240°F) creates the perfect consistency for whipping into a glossy meringue-like texture that gelatin can then stabilize as it cools. What sets homemade marshmallows apart from commercial versions is the clean, pure flavor without preservatives or artificial ingredients, the incredibly fluffy texture that’s somehow both light and substantial, and the ability to customize flavors—it’s the kind of candy-making project that feels impressive but is actually quite straightforward once you understand the key steps of temperature control and proper whipping time.