If you’ve ever had my Ultimate S’mores Cake, you already know: homemade marshmallow fluff takes any dessert to the next level. It’s light, fluffy, perfectly sweet—and way better than anything from a jar.
Whether you’re making s’mores brownies, cupcakes, or cake, this homemade marshmallow fluff adds that soft, gooey magic that makes every bite unforgettable. Today I’m showing you exactly how to make it from scratch using the same recipe I use in my s’mores cake (and so many other favorites).
Why You’ll Love This Homemade Marshmallow Fluff
- Silky smooth texture – Whipped to glossy perfection
- Torch-friendly – Toast the top for that iconic golden finish
- No gelatin – Just egg whites, sugar, corn syrup, salt and a little vanilla
- Versatile – Use it as a frosting, filling, or topping
This fluff is especially amazing when toasted! I highly recommend using a kitchen torch like this one for that beautiful caramelized finish.
Ingredients for Homemade Marshmallow Fluff
Here’s a quick overview of what you’ll need. The full recipe and quantities are included in my S’mores Cake recipe, but this guide will walk you through the process and share tips for getting it just right.
- Egg whites (room temperature)
- Granulated sugar
- Light corn syrup
- Vanilla extract
- Salt
- Water
Step-by-Step: How to Make Marshmallow Fluff
1. Heat the Sugar Mixture
Combine sugar, corn syrup, water and vanilla in a saucepan. Cook over medium heat until the sugar dissolves. Just a few minutes. Turn off the heat or keep it at low. We want it to be at or around 240 F when we add it to the eggs.
1. Whip the Egg Whites
Meanwhile, beat your egg whites and salt in a stand mixer on medium-high speed until frothy and fluffy.
3. Slowly Stream In the Syrup
With the mixer running on low to medium, slowly pour the hot sugar syrup into the egg whites. Go SLOWLY (think slow, stead stream) to avoid cooking the eggs! Once it’s all added, increase the speed to high.
4. Whip Until Glossy and Stiff
Keep whipping for about 5 minutes, until the mixture forms stiff, glossy peaks.
Tips for the Best Marshmallow Fluff
✅ Use room temp egg whites – They whip better and give you more volume
✅ Clean mixing bowl – Any fat residue can prevent the whites from whipping
✅ Don’t overheat – Stay right at 240°F for the perfect consistency (if you want to use a thermometer to check the sugar syrup)
✅ Use a kitchen torch – Toasting the fluff brings out that classic s’mores flavor (here’s my favorite torch)
Ways to Use Homemade Marshmallow Fluff
This fluff is super versatile! Here are a few of my favorite ways to use it:
- Frost the top of my S’mores Cake
- Swirl on brownies before toasting
- Fill sandwich cookies or cupcakes
- Dip graham crackers or chocolate bars for a quick dessert
- Spoon onto hot cocoa in place of marshmallows
Storage Notes
- Room Temp: Use immediately for best results
- Freezing: Not recommended—it can separate when thawed but actually stores well in the freezer or fridge when it’s TOASTED.
Why did my fluff separate?
1. Temperature issues: If the syrup is too cold or too hot, the fluff can separate.
2. Uneven Cooling: If the marshmallow fluff cools unevenly, the interior can shrink and pull away from the outer layer, creating pockets and separation. This is why a slow and steady stream of the syrup is important.
3. Under-whipping: Not whipping enough air into the mixture can lead to a less stable structure, making it prone to separation.
4. Over-whipping: However, over-whipping can cause issues too but I find this less likely to happen than under-whipping so I wouldn’t stress too much here. (This is more of an issue when you’re using gelatin, which we’re not)
5. Humidity:.High humidity can affect the stability of the marshmallow fluff and contribute to separation.
Final Thoughts
Homemade marshmallow fluff is one of those “wow” elements that makes a simple dessert feel totally next level. Once you try it, you’ll never go back to the store-bought kind! Whether you’re making a s’mores cake, brownies, or cupcakes, this easy-to-make fluff is the perfect finishing touch.
Homemade Marshmallow Fluff
Ingredients
- 3 egg whites, room temperature
- 1/4 teaspoon (1.4 g) salt
- 1/3 cup (66.6 g) sugar
- 1 cup (300 g) light karo syrup
- 2 tablespoons (29.6 g) water
- 1 tablespoon (12 g) vanilla bean paste or vanilla extract
Instructions
- In a medium size sauce pan, combine the corn syrup, sugar, water and vanilla paste. Heat over a medium flame, stirring occasionally, until the sugar is dissolved and just simmering, about 3 to 5 minutes. Turn the heat off while you move to the next step.
- In the bowl of a standing mixer with the whisk attachment, or using a hand mixer and a large mixing bowl, beat the eggs and salt until fluffy and frothy.
- With the mixer on medium speed, add a tiny bit of the hot sugar mixture to the egg whites a little at a time. (Temper the eggs – don't scramble the them). I usually have the sugar mixture in a silicone bowl that I can squeeze as I pour, in a slow, steady stream.
- Eventually, all of the sugar will be added. Turn the mixer up to high. Beat the mixture on high for about 5 minutes or until very stiff and shiny.
- Best used right away.
- Spread of the brownies and then use a kitchen torch to toast the fluff.