Brown Sugar Frosting
This frosting has been haunting me for years.
The recipe
Yield: enough to frost and fill 1 cake
Time: 1 hour
Ingredients
1 and ⅓ c (280 g) packed dark brown sugar
7 tbsp (72 g) flour
¾ c (180 g) whole milk
2 sticks salted butter (1 c or 226 g), at room temperature
Instructions
1. Place the sugar in a small pot. Sift the flour into the pot and stir both together until no lumps remain.
2. Add the milk to the sugar and flour.
3. Heat the mixture on medium-high until it begins to boil (about 10 minutes) and then let it boil for an additional 2–3 minutes. It should thicken to the consistency of a runny caramel (see the video here).
4. Transfer the mixture to a bowl, cover it, and let it cool in the fridge until it reaches room temperature (about 30 minutes).
5. After the sugar mixture is cool, place the butter in the bowl of a stand mixer fitted with the paddle attachment. Beat the butter on medium speed until it is soft and fluffy (3–5 minutes).
6. Add the sugar mixture, a large spoonful at a time, mixing well between each addition, until it is fully incorporated.
Notes and tips
You can use light brown sugar, but the frosting won’t have the full flavor you get from using dark brown.
Make sure your butter and brown sugar mixture are about the same temperature before combining them. (An instant thermometer is helpful here.) The frosting could curdle and separate if one is significantly cooler or warmer than the other.
If the frosting starts to curdle while adding the brown sugar mixture, stop. If one ingredient isn’t at room temperature, wait for it to warm up or cool down and try again. If temperature isn’t the problem, add a tablespoon of powdered sugar to the frosting. Run the mixer on high speed for a few minutes to bring it back together, then continue adding the brown sugar mixture. If you can’t get it to come together, a curdled frosting will work just fine on a sheet cake. If you’re putting it on a layer cake, frost and chill it quickly so it doesn’t slide off and store the cake in the fridge. Next time cook the sugar mixture longer on the stove.
This frosting is great on my Perfect, Easy Vanilla Cake and is a fun alternative to vanilla frosting. As you can see from the photos, I baked the vanilla cake in two 9-inch round cake pans instead of the 9x13 in the original recipe. Baking as a layer cake should take 22–25 minutes.
The frosting keeps for a few days, covered, at room temperature. So does the vanilla cake.
Special announcement
In lieu of process photos, I have a process video for this post! Thank you so very much, Abby George, for filming and editing this amazing reel and the photos for this recipe! Click the link or check out my Instagram to watch me make this frosting.
The story
I didn’t think much of it when I started developing this recipe, my first one, two years ago. My friends Allie and Joe asked me to make brown sugar cupcakes for their rehearsal dinner, and I agreed. I thought it would simply be a matter of swapping out white granulated sugar for brown in my favorite frosting recipe. It wasn’t. The frosting curdled. The guests came up to me exclaiming how good the cupcakes were; I wasn’t satisfied.
I thought I understood this frosting. It runs in my blood, having been passed down from my grandmother to my mom and from my mom to me. I’ve defended it, ardently, as the best vanilla frosting in the world, even against my mom, who slightly prefers buttercream. And when this frosting kept curdling on my mom one summer, I was the one who figured out why. It’s an emulsion, a mixture of fat (in butter) and water (in milk), which don’t usually combine. Emulsions are delicate and require their ingredients to be the same temperature. But in the summer, room temperature was much warmer than in the winter, and the difference between the warm butter and fridge-cold milk had broken the emulsion. Heating the milk a little in the microwave solved the problem. But I had no idea why the brown sugar had curdled the wedding cupcake frosting.
I hadn’t started Confessions of a Cake Snob back then, so I didn’t have answers. But I kept thinking about it. Could I make a brown sugar frosting that lived up to my standards? Every blog out there uses a buttercream frosting base (already too sweet!) and then adds a melted brown sugar mixture on top of that (I can’t even—). It had to be possible. Surely we didn’t live in a world so broken that brown sugar frosting had to be cloyingly sweet.
This spring, Allie and Joe came for a visit and wanted to bake with me. It was time to try again. I experimented with an ermine style—cooking milk, flour, and sugar into a paste and then adding that to butter. It didn’t curdle, a huge success, thanks to the stability the cooking process added to the mixture. But the frosting didn’t have enough flavor. My taste testers knew it wasn’t vanilla, but they didn’t know what it was (coffee? caramel?)—not the response I was hoping for. I tried dark brown sugar instead of light. Still not enough flavor. And I realized, with a sinking feeling, that to get enough flavor I’d have to try the very last thing I wanted to do: increase the amount of sugar. I would run the risk of making the frosting sickeningly sweet and (horror of horrors!) being like all those blogs who don’t know that salt exists. I held my nose and tried it and, miracle of miracles, there was enough salt in the butter that the frosting tasted balanced (even to me). I had the immense satisfaction of having proved all those other blogs wrong. There is always a better way than buttercream.
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