Mars Bar Brownies

Name: Mars Bar Brownies
Prep time: 5 min
Cook time: 30 min
Total time: 35 min
Ingredients: 150 g butter; 275 g (1 1/4 cups) caster sugar; 75 g (3/4 cup) cocoa powder (sifted); 2 tsp vanilla extract (or vanilla bean paste); 3 eggs (large, room temperature); 75 g (1/2 cup) plain flour (sifted); 12 fun-size Mars Bars (cut in half)

Jump to Recipe

Fudgy, gooey caramel and nougat bursts are scattered throughout these simple melt and mix Mars Bar Brownies.

This one bowl brownie recipe is always a winner - ready in just 35 minutes!

A close up of a square chocolate slice, in front of a Mars Bar.

It's no secret that a brownie recipe is one of my favourites when I need that little hit of chocolate indulgence. Whether that's my popular easy brownies made with cocoa powder, or a lavish triple chocolate brownie!

There's a brownie recipe to suit every taste as the dense and fudgy texture of a brownie combines so well with many other flavours, like brownies swirled with peanut butter, and Biscoff brownies with their malty spicy twist. Or why not indulge yourself with my boozy Baileys brownies for an 'adults only' treat?

Why You're Going To Love This Recipe

These devilishly good Mars Bar brownies are over the top - and totally worth it!

Just melt and mix - I love a one-bowl recipe, much less washing up!
Quick and easy - just 5 mins to prep your brownie mix, then only 30 mins to bake.
Slice or dessert - these versatile brownies sit equally well with a cuppa, as they do served warm with a scoop of ice cream for a luscious dessert!
Great to share - a batch of brownies also makes a lovely homemade foodie gift for someone who just needs a lift!
Make ahead – Mars Bar brownies keep well for up to 5 days in the fridge. You can freeze some too, then warm them up for dessert whenever you want something a little indulgent.
Conventional and Thermomix - both simple methods are included in the recipe card below.

Looking down on little squares of chocolate brownie, with fun sized Mars Bars around them.

What You Need

Made with basic baking ingredients, just grab a pack of fun size Mars Bars and let's get started!

Note: Scroll to the recipe card at the bottom for the ingredients quantities and full detailed method.

Butter - either salted or unsalted is fine to use in this brownie slice.
Caster sugar - fine caster sugar, or superfine sugar as it's also known as, dissolves much easier with other ingredients than regular granulated sugar does.
Cocoa powder - sifted. Whatever type of cocoa you use, make sure it’s a good quality one! Dutch processed cocoa powder lends a deep smooth flavour, but natural cocoa powder works well too, if that’s what you have on hand.
Vanilla extract - or vanilla bean paste.
Eggs - large eggs (approx 60g), at room temperature.
Plain flour - also known as all purpose flour.
Mars Bars - fun size bars, each bar cut into slices.

Equipment Required

No need for beaters or mixers, and these Mars Bar Brownies are made in just one bowl too!

20cm square baking tin - greased and lined with baking paper. Allow the edges to overhang.
Large microwave safe bowl.
Sharp knife to cut the Mars Bars with, plus a spoon and whisk.
Microwave or Thermomix - alternatively you could use a saucepan and stovetop.
Oven - my recipes specify fan-forced oven temperatures, so if you have a conventional oven, increase the temperature by between 10 and 20 degrees celsius.

Dense fudgy brownie squares on a cake stand.

Step By Step Instructions

With heavenly swirls of chocolate, caramel and nougat, Mars Bar brownies are simply regarded as 'sustenance' to any well deserving chocoholic!

Note: Scroll to the recipe card at the bottom for the ingredients quantities and full detailed method.

Step 1 - Melt The Butter

Firstly, preheat your oven to 160 degrees celsius (fan-forced). Line a 20cm square tin with baking paper, and set aside.

Place the butter into a microwave-safe bowl and heat for 1 minute until melted.

Step 2 - Dissolve Caster Sugar And Cocoa

Add the caster sugar and sifted cocoa powder to the melted butter and stir.

Sifted cocoa powder and caster sugar added to melted butter.

Heat in the microwave on 30 second bursts (50% power), stirring each time, until the caster sugar has almost dissolved. Allow the mixture to cool slightly.

Step 3 - Add The Wet Ingredients

Add the vanilla extract and the eggs and whisk together until combined.

Step 4 - Fold Through The Flour

Sift the plain flour into the bowl, and gently fold through the other ingredients.

Flour sifted over the chocolate mixture in mixing bowl.

Step 5 - Assemble And Bake

Pour half of the brownie batter into the prepared tin.

Place your sliced Mars Bars in rows over this brownie mixture.

Pieces of Mars Bar placed over brownie batter in baking tin.

Then pour the remaining brownie batter over the rest.

More brownie batter poured over the Mars Bars in baking tin.

Bake for 25-30 minutes or until cooked through - see Expert Tips.

Leave Mars Bar brownies in the tin to cool completely before removing and slicing.

Overhead shot of Mars Bar Brownie squares.

Expert Tips

A few tips to ensure the most divine Mars Bar brownies.

Careful not to overcook the brownies - otherwise they will become dry.
For fudgy/moist brownies - cook for 25-30 minutes and test with a toothpick which should come out with moist (but not wet) crumbs on it.
Being such a dense slice, brownies will continue to cook after being removed from the oven.
For an extra indulgent treat - serve Mars Bar brownies warm with a scoop of vanilla ice cream or dollop of double cream.
Storage - store Mars Bar brownies in an airtight container at room temperature for up to 4 days, or in the fridge for up to 5 days.
Freezing - freeze in an airtight container in the freezer for up to 3 months. To thaw, leave the pieces in a container in the fridge overnight, or sit them at room temperature for 1-2 hours.

Pieces of brownie, with a bite taken out of one square.

FAQs

What's a substitute for Mars Bars?

It depends where you are in the world. In Australia we have the same Mars Bar as the UK, which is caramel and nougat coated in milk chocolate.
In the US, a Milky Way is the equivalent of our Mars Bar, with their Mars Bar being more similar to a Snickers Bar, as they both contain nuts.
Moro bars are also a good substitute, but really, any of these bars are equally suitable to use in this brownie recipe as they are all very similar products.

Should I sift the cocoa and flour?

The answer is yes. In a brownie recipe the mixture does not require beating as you want the texture to be dense and fudgy. Sifting the cocoa powder and the flour, ensures that the mixture only needs to be gently folded, with no lumps!

A square of brownie with chunks of Mars bar inside.

There's a brownie for everyone, so be adventurous and do try some of the many flavour combos! M&M Brownies, fudgy Nutella Brownies.... the list goes on....

WANT EVEN MORE DELICIOUS RECIPES? Subscribe to my newsletter or follow along on Facebook or Instagram. And if you love baking, then please come and join my Facebook cooking club group or subscribe to my YouTube channel.