Brown Sugar Frosting Recipe

This brown sugar frosting is a cooked, caramel-tasting icing: you melt 1 cup butter with 1 cup light brown sugar, cool it, then beat in milk, vanilla and 2 to 3 cups powdered sugar. It takes about 45 minutes, 30 of them just cooling, and frosts a 2 layer 8 inch cake or about 18 cupcakes.

The only rule that matters is patience. Whip the base while it is still warm and the frosting splits. Wait until it is fully cool and you get a smooth, fluffy icing that tastes like toffee and holds a swirl.

The Numbers for One Batch

• Makes: enough to fill and frost a 2 layer 8 inch cake, or top about 18 cupcakes
• Time: 10 minutes prep, 5 minutes on the stove, 30 minutes cooling
• Base: 1 cup (2 sticks) unsalted butter and 1 cup packed light brown sugar, bubbled for about 2 minutes
• Stirred in off the heat: ¼ cup whole milk or heavy cream and ¼ teaspoon salt
• Powdered sugar: 2 to 3 cups, sifted, added ½ cup at a time
• Keeps: 3 days in the fridge; soften and re-whip before using

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Brown Sugar Frosting vs Caramel Icing vs Brown Sugar Buttercream

These three names get mixed up, and they are not quite the same thing. This recipe is a cooked brown sugar frosting. The butter and brown sugar boil together first, so the sugar dissolves and picks up a light caramel flavor before any powdered sugar goes in.

Old-fashioned Southern caramel icing works the same way but is usually poured warm and sets firm, almost like fudge. This version is cooled and whipped instead, so it stays soft and spreadable. An uncooked brown sugar buttercream simply beats raw brown sugar into soft butter. It is quicker, but the brown sugar never fully dissolves, and the frosting can feel slightly sandy on the tongue.

For caramel flavor without the stovetop, a salted caramel buttercream gets it from sauce. For a nutty version, try brown butter frosting, or maple frosting in maple season.

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Light or Dark Brown Sugar, Milk or Cream

Use light brown sugar, packed into the cup. It has enough molasses for a toffee flavor without taking over. When I tried dark brown sugar, the frosting tasted almost burnt, so I stick with light.

The butter is listed as softened, but it does not stay that way for long. It goes straight into a small saucepan and melts, and the brown sugar is whisked in right after. Unsalted butter lets you control the salt; the ¼ teaspoon in the recipe is what keeps the sweetness from going flat.

Whole milk gives a lighter frosting that spreads easily over cupcakes and cookies. Heavy cream makes it thicker and richer, closer to a caramel buttercream, and it holds up better between cake layers. Either way it is the same ¼ cup.

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From Saucepan to Mixer in Four Steps

Melt the butter over medium heat, add the brown sugar, and whisk without stopping. In about 2 minutes the mixture turns glossy and starts to bubble at the edges. Let it bubble for that full time. Undissolved sugar is the main reason brown sugar frosting turns gritty.

Take the pan off the heat and whisk in the milk and salt until smooth. It may hiss and look loose at first.

Once the base is completely cool, beat it on medium speed for 2 minutes. Add the sifted powdered sugar ½ cup at a time, beating well after each addition, then the vanilla. Keep beating until the frosting is fluffy and holds soft peaks. Too thick, add a small splash of milk. Too thin, add powdered sugar 1 tablespoon at a time.

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How Cool Should the Brown Sugar Base Be Before Whipping?

Fully cool, about room temperature. That usually takes 30 minutes. The base will look different by then: thicker, opaque, and closer to a soft caramel paste than a syrup. Touch the outside of the bowl or a dab of the mixture with the back of your finger. If you feel any warmth, wait.

To speed it up, pour the hot mixture into your cold mixing bowl straight away and give it a stir every 5 minutes so the edges do not set while the middle stays hot. Avoid the freezer. The butter firms unevenly and you end up with little hard flecks.

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Choosing 2, 2½ or 3 Cups of Powdered Sugar

The recipe gives a range on purpose, because the right amount depends on the job:

• About 2 cups: soft and creamy, for spreading over a sheet cake, snack cake or cookies
• About 2½ cups: sturdy enough to fill and cover a layer cake without sliding
• The full 3 cups: stiff enough to pipe tall swirls on cupcakes

Stop at 2 cups and test it on a spatula before adding more. Every extra half cup makes the frosting sweeter as well as thicker, and you cannot take sugar back out.

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If the Frosting Splits, Turns Greasy, or Feels Gritty

• Curdled, soupy or greasy: the base was still warm, or the kitchen is hot. Chill the whole bowl for 10 to 15 minutes, then beat again. It usually comes back smooth.
• Gritty: the brown sugar did not dissolve on the stove. Next time, let it bubble the full 2 minutes. For this batch, beat in a teaspoon of milk and keep mixing for another 2 to 3 minutes.
• Too stiff to spread: add milk a teaspoon at a time.
• Too sweet: add a pinch more salt rather than more butter.

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Cakes That Suit Brown Sugar Frosting

Spice is the best match. Spread it over a pumpkin spice cake, a carrot spice cake or a cinnamon cake. It is also very good on banana cake and pear cake, where the fruit softens the sweetness.

On cookies, a thin layer sets with a slight shine and a soft bite. For a plain white or yellow cake, vanilla buttercream is the lighter choice. And when you want something silkier and less sweet, ermine frosting is worth the extra step.

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Making It Ahead and Storing a Frosted Cake

Store the frosting in an airtight container in the fridge for up to 3 days. Cold butter makes it hard, so leave it on the counter for about 30 minutes, then beat it for a minute to bring back the fluffy texture. For longer storage, it can be frozen for up to a month and thawed overnight in the fridge before re-whipping.

A frosted cake is fine at cool room temperature for a day. After that, or in a warm kitchen, keep it in the fridge and take it out 30 minutes before serving so the frosting softens again.

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What Bakers Ask About This Icing

Can I make brown sugar frosting without cooking it?

You can beat brown sugar straight into soft butter, but the sugar stays grainy. Bubbling it with the butter for 2 minutes is what makes this frosting smooth.

Why did my brown sugar frosting split?

The cooked base was still warm when the powdered sugar went in. Chill the bowl for 10 to 15 minutes and beat again.

Is brown sugar frosting the same as caramel frosting?

It is close. Both start with butter and brown sugar cooked together; this one is cooled and whipped with powdered sugar, so it stays fluffy instead of setting firm.