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Marshmallow brownie

Updated: Tue, 22 August, 2023

Homemade marshmallow brownie with marshmallow made from scratch. You’ll be happy to hear that you can make those brownies with Marshmallow Fluff instead of fighting with hot syrup and meringue for the whole afternoon.

marshmallow brownie

Can you make marshmallow at home?

The sucker for punishment that I undoubtedly am, I endeavoured to make marshmallow from scratch. To be truthful, I’d had a stack of egg whites in the freezer, tidily decanted two at a time into freezer bags, waiting for inspiration after only so many meringues that you can bake.

It was fun. Not the kind of fun that I’d want to repeat too soon though.

marshmallow fluff

Marshmallow adventure

Marshmallow is basically a meringue made with hot sugar syrup, instead of caster or icing sugar. In addition, the sugar syrup is made with corn syrup cooked with sugar, to be extra-syrupy, and that makes everything stickier and generally messy.

Making the syrup however is a doddle if you’re an experienced jammer (I am), otherwise it might seem to last forever.

sugar syrup

But that’s doable: the real fun begins when you pour the syrup into the beaten egg whites ‘in a steady slow stream’, as recipes instruct.

If you’re doing it with a handheld mixer, you’re stuffed – and don’t even dream of whisking it by hand. The coordination of your mixer hand with the ‘slow steady stream’ hand, no matter which task you do with your dominant hand, is near impossible.

The whole project is bound to end in splatting the ‘steady stream’ all over your hands – and I can tell you hot sugar burns are quite unpleasant – or ricocheting it off the mixer paddles all over the kitchen.

streaky brownie with marshmallow

Can I not use standing mixer?

The standing mixer is a godsend in most circumstances but here, not so much.

The slow steady stream will either bounce off the whirling attachment (see above) or trickle down the walls of the bowl, nicely solidifying on its way.

If you somehow manage to send the slow steady into that magic square centimetre between the paddle and the bowl wall, at the end of the exercise you’ll find it pooled at the bottom hiding underneath the partly made marshmallow.

You’ll then need to dip the whole bowl in a pan of hot water to melt the syrup (of course it set in the meantime) and try to salvage the mixture by beating it furiously again whereby it may well give up and collapse into clumps.

So yes, go on the above adventure making good note of my caveats or buy Marshmallow Fluff if you are sensible and it’s available. It will pay off though (especially if you just buy the Fluff) because it is absolutely the best brownie in the whole wide world.

homemade marshmallow fluff

What about the brownie?

Weirdly, the original recipe from Salt & Straw makes the brownie merely as a chopped up addition to vanilla and brownie ice cream. Some people! All that trouble only to churn the outcome in ice cream, thus making the flavour flat and indiscernible.

But whatever you do with your baked brownie, making it is a walk in the park compared to the devilish marshmallow fluff.

Butter and chocolate melt in a double boiler, sugar and eggs get beaten until pale and fluffy, then both are combined by pouring chocolate butter in a steady slow stream (hehe).

butter and chocolate

Dry ingredients can be just folded in and there is double cream added at the end (in a slow steady stream of course) which will make the brownie incredibly tender and rich.

brownie batter

The marshmallow or the Fluff is the last addition and its purpose is to create wonderfully sickly, gooey streaks in the cake.

mixing in marshmallow

Baking is the matter of twenty minutes or so, until the surface cracks and the edges start to pull away.

baked brownie

It’s gorgeous, it’s rewarding, it’s the brownie of dreams, but is it worth the toil of making your own fluff – that’s debatable.

marshmallow brownie from salt & straw

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brownie before cutting

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gooey fudgy brownie

Marshmallow brownie

Servings: makes 16 browniesTime: 1 hour plus making marshmallow


  • For the marshmallow:
  • 80g (13 cup) caster sugar
  • 120g (13 cup) corn syrup
  • 40g (3 tbsp) water
  • 2 egg whites (about 80g)
  • 12 tsp cream of tartar
  • vanilla extract (optional)
  • For the brownie:
  • 115g (1 stick) unsalted butter
  • 130g (34 cup) dark chocolate pieces
  • 2 large eggs
  • 150g (34 cup) caster sugar
  • 65g (12 cup) plain flour
  • 25g (14 cup) cocoa powder
  • 1 tsp fine salt
  • 120ml (12 cup) double cream
  • 240ml (1 cup) marshmallow (from above, or shop-bought Marshmallow Fluff)


1. You can use ready made Marshmallow Fluff if you can buy it, in which case go straight to point 4. To make your own, place the sugar, corn syrup and water in a small saucepan over very low heat, stirring until the sugar fully dissolves. Stop stirring and bring to a simmer. You can cover the pan with a lid to avoid the syrup crystallising on the walls of the pan. Cook until the temperature of the syrup reaches 120C/240F, or the mixture passes the jam test (drop a blob onto ice cold plate and check if it sets).

2. In the meantime beat the egg whites with a handheld or in a standing mixer with a balloon attachment until foamy; add the cream of tartar and beat until soft peaks.

3. When the syrup reaches the desired temperature take it off the heat and pour into the egg whites in a slow steady stream, trying to avoid the walls of the bowl (it will cool down and set on them). Keep beating until the syrup is used up and continue for about 5-10 minutes at high speed until the mix is really fluffy and airy. At the end beat in the vanilla extract if using. Measure out 1 cup of the fluff and keep the rest in airtight container to top desserts or cakes; or to make mini meringues out of it.

4. For the brownie, melt the butter and chocolate together over bain-marie (a bowl suspended over a pan with some water simmering at the bottom). Let it cool down slightly while you preheat the oven to 180C/350F/gas 4 and prepare a 23 x 23cm (9 x 9 inch) square brownie tin by lining it with parchment or thoroughly buttering and flouring.

5. Beat the eggs with the sugar until pale and airy and pour the chocolate mix into them, beating at low speed, in a steady slow stream.

6. Stir the flour, cocoa and salt together in a separate bowl and add to the brownie batter; mix until just combined. Drizzle in the cream and mix until just combined. Scrape down the sides and fold in the marshmallow roughly so that streaks remain.

7. Pour the mix into the tin and bake for 25-30 minutes, until cracks appear on the surface and a skewer inserted into the centre comes out clean.

8. Cool completely in the tin, then cut into squares with a serrated knife.

Originally published: Thu, 26 September, 2019

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Hello! I'm Anna Gaze, the Cuisine Fiend. Welcome to my recipe collection.

I have lots of recipes for you to choose from: healthy or indulgent, easy or more challenging, quick or involved - but always tasty.


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