Pin it
I discovered these Thin Mint Marshmallow Brownies during Girl Scout cookie season last year when I had three boxes of Thin Mints staring me down from the pantry. I could have just eaten them straight from the box like a normal person, but where's the fun in that? Instead, I decided to transform them into something even more ridiculously indulgent.
My normally reserved father-in-law took one bite of these and declared, "Good Lord, woman! Are you trying to kill me?" before immediately cutting himself a second piece. This from a man who typically describes desserts as either "fine" or "too sweet." I consider that high praise.
What Goes In The Layers
- Fudgy brownies: Box mix works but homemade with brown butter is next level
- Marshmallow creme: That magical fluffy stuff from the jar
- A tiny bit of peppermint extract: The secret is RESTRAINT
- Crushed Thin Mints: Because double mint is double good
- More chocolate: Because why stop at two chocolate layers?
Pin it
Brownie Magic Method
- Brownie Base Brilliance
- Whether you go homemade or box mix, the key is getting that perfect fudgy texture. For homemade, I highly recommend browning the butter first - it adds this nutty, caramelized flavor that elevates everything. Either way, don't overbake! You want these slightly underdone when you pull them out of the oven since they'll continue cooking as they cool. A toothpick should come out with a few moist crumbs still clinging to it.
- Marshmallow Mastery
- Here's where people mess up - they add way too much peppermint extract. Listen, this stuff is potent. I'm talking literally 3-4 drops, max. Stir it into the marshmallow creme BEFORE spreading it on the cooled brownies. And don't try to spread it when the brownies are still warm or you'll have a melty disaster on your hands. The trick to getting a nice even layer is wetting your spatula with a little hot water first - the marshmallow won't stick as much.
- Cookie Crushing Strategy
- Don't pulverize the Thin Mints into dust - you want recognizable chunks. I put them in a ziplock bag and smash them with a rolling pin, aiming for pieces about the size of a dime. Some will be smaller, some larger - that variety in texture is part of what makes these brownies amazing. Sprinkle them over the marshmallow layer while it's still tacky so they stick.
- Final Chocolate Drizzle
- This step is optional but adds that extra wow factor. Melt some chocolate chips with a tiny bit of shortening or coconut oil for smoothness, then drizzle over the top. You can get fancy with a piping bag, but I just use a spoon and go back and forth quickly for a Jackson Pollock effect. Let this set before cutting for the cleanest slices.
Last month I brought these to a book club meeting, and one friend who was "watching what she eats" initially declined. Twenty minutes later, I caught her in the kitchen cutting herself a piece "just to taste." She then proceeded to text me at midnight asking for the recipe because she "couldn't stop thinking about them." That's the power of these brownies - they haunt your dreams.
Seasonal Variations
When it's not Girl Scout cookie season, use Keebler Grasshoppers or Mint Oreos instead. Around Christmas, crush up candy canes for the topping instead of cookies. For St. Patrick's Day, add a drop of green food coloring to the marshmallow layer. In summer, add some chopped fresh mint leaves to the brownie batter for a refreshing twist.
Serving Suggestions
These are rich, so cut them into small squares - people can always come back for seconds (and they will). For an over-the-top dessert, serve warm with vanilla ice cream. They make a beautiful addition to a dessert tray - the contrast of the dark brownie, white marshmallow, and cookie pieces is visually stunning.
Trouble-Shooting Tips
If your marshmallow layer is sliding off, the brownies were probably still warm when you added it. Pop the whole thing in the freezer for 15 minutes to set. If the brownies seem too gooey to cut, refrigerate them first. If the mint flavor is too strong (it happens to the best of us), balance it with a drizzle of hot fudge before serving.
Pin it
I've made these Thin Mint Marshmallow Brownies several times now, tweaking the recipe slightly each time, and they never fail to impress. There's something about the combination of chocolate, mint, and marshmallow that taps into childhood nostalgia while still feeling grown-up enough for any occasion. Plus, they're a great way to support your local Girl Scout troop while simultaneously ensuring you never fit into your pants again. Worth it.
Frequently Asked Questions
- → Can I use regular Oreos instead of Thin Mints?
- Yes, but you'll want to add a bit more peppermint extract to the marshmallow layer to get that minty flavor. Regular Oreos with 1/4 teaspoon mint extract works great.
- → Why brown the butter for the brownies?
- Browning the butter adds a nutty, caramel-like richness that makes these brownies extra special. You can skip this step if you're short on time.
- → Can I make these ahead of time?
- Absolutely! They actually get better after a day in the fridge. Just store them in an airtight container for up to 4 days.
- → Can I freeze these brownies?
- Yes, but freeze them before adding the marshmallow and cookie topping. The marshmallow layer doesn't freeze well and can become watery when thawed.
- → The mint flavor is too strong. How can I fix it?
- Peppermint extract is potent! If you already mixed it in and it's too strong, try adding more marshmallow creme to dilute it. Next time, start with just a drop or two.