If you’re looking for the ultimate dessert that combines gooey marshmallows, rich chocolate, crunchy graham crackers, and the subtle tang of sourdough discard, these Sourdough S’mores Cookie Bars are guaranteed to become a favorite. They capture all the nostalgic flavors of a campfire s’more without needing a fire pit. The sourdough discard adds depth of flavor and creates an incredibly soft, chewy cookie bar that stays fresh for days.
These bars are perfect for family gatherings, potlucks, bake sales, or whenever you’re craving something sweet and comforting. Best of all, they’re simple to make and a fantastic way to use up extra sourdough discard.
Why You’ll Love This Recipe
- Great use for sourdough discard
- Soft and chewy texture
- Loaded with chocolate and marshmallows
- Easy one-pan dessert
- Perfect for sharing
- Tastes even better the next day
Ingredients
For the Cookie Bar Base
- ½ cup (113g) unsalted butter, softened
- ¾ cup (150g) brown sugar
- ¼ cup (50g) granulated sugar
- 1 large egg
- ½ cup (120g) sourdough discard
- 1 teaspoon vanilla extract
- 1¾ cups (220g) all-purpose flour
- ½ teaspoon baking soda
- ½ teaspoon salt
For the S’mores Filling
- 1 cup milk chocolate chips
- 1 cup mini marshmallows
- 6 graham crackers, roughly broken into pieces
- 1 regular-sized milk chocolate bar, chopped
Instructions
Step 1: Prepare the Pan
Preheat your oven to 350°F (175°C).
Line an 8×8-inch baking pan with parchment paper, leaving some overhang on the sides. This makes it easy to lift the bars out after baking.
Step 2: Make the Cookie Dough
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 2 to 3 minutes.
Add the egg, sourdough discard, and vanilla extract. Mix until smooth and fully combined.
In a separate bowl, whisk together the flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing just until a soft cookie dough forms. Avoid overmixing.
Step 3: Assemble the Layers
Press about two-thirds of the cookie dough evenly into the prepared baking pan.
Sprinkle the broken graham crackers across the dough layer.
Add the chocolate chips and chopped chocolate bar evenly over the graham crackers.
Scatter the mini marshmallows over the chocolate.
Take the remaining cookie dough and flatten small portions between your fingers. Place them across the top of the filling. It’s okay if some marshmallows and chocolate remain visible.
Step 4: Bake
Bake for 28 to 33 minutes, or until the top is lightly golden brown and the edges are set.
The center may still look slightly soft, but it will continue to firm up as it cools.
Step 5: Cool and Slice
Allow the bars to cool completely in the pan for at least 1 hour.
Use the parchment paper to lift the bars from the pan and transfer them to a cutting board.
Slice into 12 to 16 squares and serve.
Tips for Success
Use Room Temperature Ingredients
Butter, egg, and sourdough discard blend more smoothly when they’re at room temperature, creating a better texture.
Don’t Overbake
The bars should still be slightly soft in the center when removed from the oven. Overbaking can make them dry.
Let Them Cool Completely
The melted marshmallows and chocolate need time to set. Cutting too early can result in messy bars.
Use Active or Discard Starter
Both active starter and unfed discard work well. Discard gives the bars a slightly more pronounced sourdough flavor.
Fun Variations
Peanut Butter S’mores Bars
Add ½ cup peanut butter chips to the filling for a delicious twist.
Dark Chocolate Version
Replace milk chocolate with dark chocolate for a richer flavor.
Double Chocolate
Mix ¼ cup cocoa powder into the dough and use chocolate chunks throughout.
Salted Caramel S’mores Bars
Drizzle caramel sauce over the marshmallows before baking and sprinkle flaky sea salt on top after baking.
Storage
Store the bars in an airtight container at room temperature for up to 4 days.
For longer storage, refrigerate for up to one week. Allow them to come to room temperature before serving for the best texture.
These bars also freeze beautifully. Wrap individual pieces in plastic wrap and place them in a freezer-safe container for up to 3 months.
Serving Suggestions
These cookie bars are delicious on their own, but they become even more irresistible when served:
- Warm with a scoop of vanilla ice cream
- Drizzled with melted chocolate
- Alongside a hot cup of coffee
- With a cold glass of milk
- As part of a dessert platter for parties
