S'mores Cookie Bars

These indulgent s'mores cookie bars combine two beloved treats—gooey chocolate chip cookies and sticky marshmallow fluff—into one irresistible dessert. With a buttery cookie base, a generous layer of marshmallow, and another cookie layer on top, they deliver all the campfire flavors without the actual fire. I've tested this recipe numerous times to perfect it, and the result is simply outstanding.

The first time I brought these to a neighborhood gathering, they vanished within minutes. One of my friends even texted me at midnight asking for the recipe because she couldn't stop thinking about them! While they're especially fitting for fall bonfires and Halloween, I find myself making them throughout the year whenever the s'mores craving strikes.

Ingredients

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• 250g butter, softened: You can use either baking spread or unsalted block butter at room temperature. This creates the rich, buttery foundation for our cookie layers.
• 150g granulated sugar: Provides the perfect level of sweetness and helps create those slightly crisp edges.
• 150g light brown soft sugar: Adds moisture and a deeper caramel-like flavor that's essential for that classic cookie taste.
• 1 medium egg: Binds everything together while adding just the right amount of structure. A large egg works fine too.
• 1 teaspoon vanilla extract: Enhances all the flavors and adds that warm, aromatic note.
• 300g plain flour: The main structure of our cookie bars. Measure accurately for best results.
• 30g cornflour: This secret ingredient gives the cookies that perfect soft, tender texture.
• 1 teaspoon bicarbonate of soda: Essential for that slight rise and perfect cookie texture.
• 1 teaspoon sea salt: Balances the sweetness and enhances the chocolate flavor. Chunky sea salt adds occasional bursts of flavor.
• 200g chocolate chips or chunks: Use milk, dark, or a combination. Chop bars for varying sizes of chocolate throughout.
• 200g marshmallow fluff: The star of the show! Store-bought works perfectly, or make your own if you're feeling ambitious.

Step-by-Step Instructions

Step 1:

Prepare your baking space - Preheat your oven to 180°C (160°C fan/350°F). Line a 9×9-inch square baking tin with parchment paper, leaving overhang on the sides for easy removal later.

Step 2:

Create the cookie dough base - In a large mixing bowl, combine the softened butter with both white and brown sugars. Beat with an electric mixer for 1-2 minutes until light and fluffy. Add the egg and vanilla extract, then beat again until fully incorporated and smooth.

Step 3:

Incorporate the dry ingredients - Add the plain flour, cornflour, bicarbonate of soda, and sea salt to the bowl. Mix on low speed until just combined—be careful not to overmix. The dough should come together but still look a bit soft.

Step 4:

Add the chocolate - Fold in your chocolate chips or chunks using a rubber spatula, distributing them evenly throughout the dough. The dough will be quite thick at this point—this is perfect for cookie bars!

Step 5:

Divide the dough - Split the cookie dough into two uneven portions: about two-thirds and one-third. This doesn't need to be exact, but the bottom layer should be thicker than the top.

Step 6:

Create the first layer - Press the larger portion of dough into your prepared baking tin, creating an even layer across the bottom. Use your fingertips or the back of a spoon to gently press it down, ensuring there are no gaps or holes.

Step 7:

Prepare the marshmallow layer - If using store-bought marshmallow fluff, microwave the tub for about 20 seconds to make it more spreadable. For homemade fluff, ensure it's at room temperature. Carefully spread the marshmallow fluff over the first cookie layer, leaving a small border around the edges if possible.

Step 8:

Add the top cookie layer - Take the remaining third of cookie dough and break it into small pieces. Place these pieces all over the marshmallow layer, trying to cover as much surface as possible. Don't worry if some marshmallow is still visible—this creates those lovely gooey pockets in the finished bars.

Step 9:

Bake to perfection - Place the tin in your preheated oven and bake for 25-30 minutes until the top is golden brown and the edges are set. The center may still look slightly soft—this is perfect for gooey cookie bars.

Step 10:

Cool completely - Allow the bars to cool in the tin for at least 1 hour before attempting to remove or cut them. The marshmallow needs time to set, and cutting too soon will result in a very messy (though delicious) situation.

Step 11:

Slice and serve - Once cooled, use the parchment paper overhang to lift the entire slab out of the tin. Place on a cutting board and cut into 16 squares with a sharp knife. For cleaner cuts, wipe the knife between slices.

The Magic of Marshmallow Fluff

What makes these cookie bars special is the marshmallow fluff layer. Unlike regular marshmallows that would melt away during baking, marshmallow fluff maintains its gooey, stretchy texture, creating that authentic s'mores experience. The fluff also helps keep the cookies moist for days, preventing them from drying out the way regular cookies might.

The Perfect Cookie Base

This cookie dough is my tried-and-true recipe that I've used in countless variations. The combination of white and brown sugars creates the perfect balance of crisp edges and chewy centers. The addition of cornflour might seem unusual, but it's my secret weapon for creating that irresistibly soft texture that stays tender for days.

Chocolate Selection Matters

While any chocolate works well in these bars, I find that a mix of milk and dark chocolate creates the most complex flavor. Chopping chocolate bars rather than using chips gives you varying sizes of chocolate throughout the bars—some melty pockets and some chunky pieces—adding wonderful texture contrast.

Storage and Serving Suggestions

These bars keep beautifully at room temperature in an airtight container for 4-5 days, though I doubt they'll last that long! For an extra-special treat, warm individual bars in the microwave for 10-15 seconds before serving. This slightly melts the chocolate and makes the marshmallow even gooier—truly the ultimate s'mores experience.

I learned through multiple test batches that patience is key with these bars. My first attempt, I was too eager and cut them while still warm, resulting in a delicious but messy situation with marshmallow everywhere! Allowing them to cool completely makes all the difference in how they slice and serve.

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After making these countless times, I've discovered that chilling the assembled but unbaked bars for 20 minutes before baking helps the layers maintain their definition better. While not necessary, it's a trick worth trying if you have the time and want picture-perfect bars.

These S'mores Cookie Bars bring together the best of both worlds—the comfort of homemade cookies with the nostalgic joy of s'mores. They're perfect for any gathering, from summer picnics to winter holiday parties, and are guaranteed to disappear quickly. The combination of buttery cookie, gooey marshmallow, and melty chocolate creates a treat that's impossible to resist!

Frequently Asked Questions

→ Can I use regular marshmallows instead of marshmallow fluff?

Regular marshmallows will boil and mostly disappear into the cookie dough. For best results, stick with marshmallow fluff which keeps its gooey texture after baking.

→ Where do I find marshmallow fluff?

Marshmallow fluff is usually found in the supermarket near Nutella and jams. It's becoming widely available in most grocery stores.

→ What type of chocolate works best in these bars?

You can use any type you prefer! Dark, milk, or white chocolate chips all work well. You can even try flavored chocolate for a unique twist.

→ How should I serve these bars?

They're delicious at room temperature, but try microwaving them for 10-15 seconds for an extra gooey treat. They're also amazing with a scoop of vanilla ice cream!

→ How long do these cookie bars stay fresh?

Store them in an airtight container at room temperature for up to 4 days, though they're usually devoured long before then!