Chocolate Mint Brownie Slice

Chocolate brownie and mint join forces to create this amazing traybake. A must for all chocolate mint fans.


I have a bit of sweet tooth. Ok so the Husband is currently guffawing into his tea. Fine, it’s maybe more than a bit. It’s maybe more like a whole mouthful of sweet teeth. I keep seeing all these tv programmes about how bad sugar is for you, and the celebrities giving it up left, right and centre. And I have tried. But I can’t. I just can’t.

I have a particular fondness for cake. So much so, that just over a year ago I started a cake club with a few of my friends. We started off trying new things, having a theme each month, and experimenting with what we made. That has since turned into just any excuse for us to get together of an evening once a month, without any screaming children, drink some wine, and eat cake. Needs must.


So this was my last bake for Cake Club (it deserves the capitals). I’m an absolute sucker for chocolate mint. I’d happily chomp my way through a box of After Eights given half a chance – or if the guilt didn’t set in. So I’d seen these knocking about Pinterest for a while, and decided it was time to give them a go. I used my own recipe for the brownie, and made something up for the mint layer. Thankfully it worked, and the result was a pretty god damn good slice of deliciousness.



200g dark chocolate, 70% cocoa
250g unsalted butter, softened
300g caster sugar
100g plain flour
50g cocoa
1/2 tsp salt
1/2 tsp baking powder
3 eggs
1 tbsp vanilla


1. Line and grease a 9″ tin, or a similarly sized tin. You can see that by ‘line’, I was highly precise. I used some groundnut oil to grease, but you could use spray oil or melted butter.

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2. Melt the dark chocolate, either in the microwave in 30 second bursts (stir well between each time, as chocolate burns pretty easily), or in a bowl over a pan of simmering water on the cooker. Set this aside to cool slightly.

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3. Cream the butter with the sugar until light and fluffy. I used a hand mixer this time which takes a bit more mixing than my standing mixer, but this is what adds lightness to your mixture so you can’t really be half-arsed about it. Then beat in the 3 eggs and finally the vanilla.


4. In a separate bowl sieve the flour, cocoa, salt and baking powder. It’s best to sieve these ingredients to avoid any lumps.

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5. Add the melted chocolate to the butter/sugar mixture and fold in. Try to be as gentle as possible to retain as much air in the mixture as possible.

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6. Add the dry ingredients and again fold everything in together. This is quite a thick brownie mixture – often brownie mixes are fairly liquid.


7. Fill your pre-lined tin with this mixture and smooth out as much as possible. It’s so thick this mixture, that it takes a bit of effort to get it into the corners, and evenly spread – the baking parchment moves about a lot and makes it quite fiddly, but the parchment is a godsend when you have to take the slice out of the tin.


8. Bake this for 30 minutes at 160°C(fan)/300°F/Gas 2. Don’t worry about whether the centre is cooked or any such gubbins at this point. Just trust the process. Let the brownie cool completely on a wire rack (still in the tin), then put it in the fridge for at least an hour to fully cool. The trick with brownie is to cook it at a lowish heat until its not quite done, then cool it completely once out so that it retains that lovely gooey middle we all love, but you can slice it fairly easily.

Mint Layer:

100g unsalted butter, softened
400g icing sugar
3 tbsp milk
3 tsp peppermint extract
green colouring


9. Start to beat the butter and icing sugar (no need to sieve) together, then add the remaining ingredients and beat and beat and beat some more, until you have a lovely light fluffy minty green buttercream. This is where standing mixers come into their own – I had no idea buttercream could be so fluffy and gorgeous until I owned my mixer. However, if you don’t have one, at least use a hand mixer (beg, borrow or steal if necessary) and beat it until you’re thoroughly bored. Then beat it some more. I promise you, the more you beat it, the better it will be.


10. Layer the mint buttercream onto the brownie (still in the tin) and spread it evenly to fully cover the bottom layer. Chuck this into the fridge for at least half an hour to let the buttercream harden.


In case you were wondering, I used the above peppermint extract (mine is from Lakeland, but I think most supermarkets will have some) and green colouring (it’s a paste because that’s what I use for cake decoration, but you could use any green colouring you can get your hands on). If you’re like my lovely friend Sarah, who goes loopy at the merest hint of colouring, you can leave it out completely. It’ll still taste exactly the same, it just won’t have that amazing 70’s vibe about it.

Chocolate Top Coat:

200g milk chocolate
15g unsalted butter

11. Melt the chocolate together with the butter, again either in the microwave or in a bowl over simmering water. Pour this over the mint layer and spread to fully cover. I topped mine with some Aero mint balls for decoration.


12. Leave the chocolate to cool and set at room temperature, then take the whole thing out of the tin (using the paper) and slice into whatever sized pieces you desire.


I found that the longer this was left, the mintier it seemed to get. Not that it lasted that long. With the three layers, its not the quickest of traybakes to make, but its one of those first bakes that I’ll most definitely be baking again. It is truly worth it.

Anyway, I promised myself some Ben’n’Jerry’s once I’d finished this blog. So I’ll be off….

Happy cooking!

Author: Sarah Margetts

Busy mum of four, cooking up a storm.