How to make the perfect s’mores—with science

S'more is s'more.
hand holding a smore in the woods
S'mores are definitely one of the top 3 reasons to go camping. Kenrick Mills / Unsplash

A perfectly golden brown exterior, a gooey center, and a piece of smooth, dripping chocolate. There’s something special about s’mores that make them warm and cozy, and an indispensable snack at any campfire. And if there’s one thing I excel at, that’s making the perfect one.

The key is to heat up your marshmallows just right—but what that means exactly is often a controversial point of discussion around the campfire. If you like your white fluffy treats burned to a crisp and still cold on the inside, that’s your prerogative. On the other hand, if you prefer the warm gooeyness of a perfectly chocolatey s’more, you can use science to make it happen.

Making good s’mores is all about technique

To make the perfectly roasted marshmallow you’ve got to be patient, says long-time s’mores connoisseur Courtney Gaine, president and CEO of The Sugar Association. Rush the process and your marshmallow will instantly catch on fire, resulting in a treat that’s charred on the outside while still cold on the inside.

Take your time as you toast. Start with the low and slow method: resist the urge to get close to the heat source and instead hover your skewered marshmallow over the hot coals near the edge of the fire, or six to eight inches above the flames. Rotate your stick to facilitate even cooking. Keep it there for three to five minutes, or until the marshmallow starts to puff and turn golden.

[Related: How to make the most perfect s’mores ever]

Similarly to cooking meat, you want to make sure the inside gets warm before the outside burns. After all, it’s the gooey center of the white fluff that makes a s’more so delightful, and this is exactly what this cooking method accomplishes. First, the relatively low heat (90 to 95 degrees Fahrenheit) breaks down the gelatin in the marshmallow almost immediately. The temperature also expands the air pockets within the sugary treat, making it larger and softer as it warms, turning the center into a sweet goo. Lastly, heat breaks the bounds linking fructose and glucose molecules to sugar, allowing the marshmallow to expand further and develop more nuanced flavors.

Next, when the marshmallow starts to puff up, move it closer to the fire. You want to place it where the tips of the flames may only lick at the mallow, not engulf it. At a temperature nearing 250 degrees, the Maillard reaction will kick off. This chemical process occurs when the amino acids from the gelatin and heated sugar interact, causing the exterior of the marshmallow to start browning and a developing toasty flavor.

At this point, your treat may start to sag or spin around your roasting stick. This means that it’s perfectly soft on the inside and it’s time to caramelize the outside for that subtle crispiness around the edges. This means it’s time to move your mallow next to the hotter base of the flame or nearer the hot coals where the caramelization process can occur at temperatures around 320 degrees. As sugar breaks down under heat and you see your treat begin to bubble and brown even more, new compounds will arise, resulting in an even darker exterior. 

This process won’t take more than 10 or 20 seconds, so keep a watchful eye and take care not to catch your marshmallow on fire—unless that’s what you want. 

When the exterior turns a dappled medium to dark brown, it’s s’mores time.

How to assemble the perfect s’more

When you’re ready to put your s’more together, slide the warm marshmallow off the stick onto a graham cracker topped with a piece of chocolate. But move fast—because while milk chocolate melts easily, at around 90 to 95 degrees, if the air temperature is even slightly lower than that, your marshmallow will cool too quickly and won’t be able to melt the chocolate. This is why Gaine recommends prepping all your ingredients beforehand so you’re ready to assemble as soon as your mallow is toasted.

When you release the warm white fluff, the milk chocolate will soften quickly. If you, like Gaine, prefer your chocolate to fight back when you bite into it, let your marshmallow cool for 20 seconds before transferring it from your roasting stick. You can also get this crunch more easly by opting for dark chocolate. This variety has a higher melting point (around 110 to 115 degrees) due to its lower fat and sugar content. This allows it to stay solid for longer.

Finally, after you’ve given the mallow a few seconds to cool to ensure you won’t burn your mouth, chow down and enjoy. And keep some napkins handy to clean up the sticky, chocolatey mess.

Upgrade your fixings

While the classic s’more may be beautiful in its simplicity—marshmallow, milk chocolate, graham crackers—a s’more can be so much more. Gaine is a traditionalist when it comes to the three basic elements, but in my opinion, you can definitely play around with more sophisticated or delectable ingredients.

My favorite upgrade is to ditch the chocolate in exchange for a peanut butter cup. Once you experience the warm combination of melted chocolate and soft peanut butter you’ll never look back. You can also try flavored chocolate like raspberry, coffee, or caramel, to add more of a novel touch.

[Related: Stay-at-home science project: Bake s’mores using the power of the sun]

You can also add to the classic by swiping a spoonful of peanut butter, jam, or hazelnut spread onto your graham crackers before adding the marshmallow. Alternatively, swap the graham crackers for chocolate chip cookies, fudge-covered graham crackers that negate the need for extra chocolate (or add even more), or my favorite cookie swap: chocolate peanut-butter cookies like Girl Scout’s Tagalongs.

Needless to say, the possibilities are endless, especially given the abundance of vegan, gluten-free, and allergen-friendly s’mores ingredients. And as long as your marshmallow doesn’t turn into a bunch of burnt sugar, you can enjoy this delicious outdoorsy treat however you like.