Kiwi frosting is a buttery, lightly tangy topping made with fresh kiwi that is cooked down before it is mixed into the frosting. Reducing the fruit concentrates its flavor and removes excess moisture, while cooking also deactivates kiwi’s protein-breaking enzyme, helping the buttercream stay smooth.
Ingredients
- 1 cup peeled, finely diced kiwi (about 180 g, usually 3 medium kiwis)
- 1 cup unsalted butter, softened but not melted (226 g)
- 4 cups powdered sugar, sifted if lumpy (480 g)
- 1 teaspoon vanilla extract (5 ml)
- ⅛ teaspoon fine salt (about 0.7 g)
- 1–2 teaspoons milk or cream, only if needed to loosen the frosting (5–10 ml)
Instructions
- Cook the kiwi. Put the diced kiwi in a small, nonreactive saucepan and mash it with a fork or potato masher. Set the pan over medium heat until the fruit begins to bubble, then lower the heat to maintain a gentle simmer. Cook uncovered for about 15 minutes, stirring often and mashing any larger pieces. The fruit should become thick and spoonable, with about ⅓ cup (80 ml) of concentrated puree remaining. If it is still loose and watery, simmer it a little longer; the final volume matters more than the exact time.
- Cool the puree completely. Scrape the kiwi into a shallow bowl so it cools faster. Leave it at room temperature for about 45 minutes, stirring once or twice. It must be fully cool before it goes into the butter, or the buttercream can turn soft and greasy. For a smoother finish, press the cooked puree through a fine-mesh sieve to remove the seeds; leaving them in gives the frosting a natural, speckled look.
- Beat the butter. Place the softened butter in a large mixing bowl. Beat with a hand mixer or stand mixer on medium speed for 2–3 minutes, scraping down the sides once, until it looks pale and creamy. If the butter is cold and firm, let it soften a little longer rather than trying to warm it in the microwave. Melted butter will make the frosting difficult to whip and hold its shape.
- Add the sugar and flavorings. Add the powdered sugar in three or four additions, mixing on low speed after each one to prevent a cloud of sugar from escaping the bowl. Once it is mostly incorporated, add the vanilla and salt. Beat on medium for about 1 minute, then scrape the bowl and paddle or beaters so no pocket of plain butter remains at the bottom.
- Mix in the kiwi gradually. Add the cooled puree 1 tablespoon at a time, beating briefly after each addition. Start with 3 tablespoons, then check the taste and texture before adding more. Stop when the frosting has a noticeable fresh-fruit tang and is thick enough to hold a soft peak. The full reduced amount can be used if the frosting remains firm, but adding it gradually gives you control over the moisture and flavor.
- Adjust and finish. Beat the frosting for 1–2 minutes until smooth and fluffy. If it is too stiff to spread, add milk or cream ½ teaspoon at a time. If it is too soft, mix in powdered sugar 1 tablespoon at a time or refrigerate the bowl for 15–20 minutes, then beat briefly again. Use it to frost 12 cupcakes or a cooled cake.
Tips
- Choose ripe fruit, not overripe fruit. A ripe kiwi yields slightly when pressed and tastes sweet-tart. Very hard fruit can taste sharp, while bruised or mushy fruit may bring excess liquid and a dull flavor. Peel it with a small knife or vegetable peeler, and dice it finely so it cooks evenly.
- Measure the puree after reducing. Kiwi sizes and juiciness vary, so the stated 15 minutes is a guide rather than a guarantee. The useful cue is a thick puree reduced to roughly ⅓ cup. A watery puree can thin the buttercream before it contributes enough fruit flavor; simmer it longer, then cool it fully.
- Keep the butter soft, not warm. It should indent when pressed but still hold its shape. If your room is hot, work quickly and chill the finished frosting briefly if it seems loose. Avoid adding warm puree or beating for a long time after the frosting is already fluffy, as either can make the texture slack.
- Add color only if you want it. Natural kiwi usually gives buttercream a subtle ivory-green tint rather than a vivid green. For a stronger shade, use a small amount of gel food coloring. Liquid coloring can loosen the frosting, so add it sparingly and adjust the consistency only after the color is mixed in.
Serving Suggestions
Spread this frosting on vanilla, lemon, coconut, or white chocolate cupcakes, where its tart fruit note balances a sweet cake. It also works on a simple sheet cake or between the layers of a cooled sponge cake. The recipe makes enough for a generous swirl on 12 cupcakes; for a thin layer across a large cake, you may have some left over, while elaborate piping or a tall layer cake may need a larger batch.
For a neat finish, use an offset spatula to make soft swirls or transfer the frosting to a piping bag fitted with a broad round or star tip. Keep the kiwi flavor in mind when choosing decorations: sliced fresh kiwi, lime zest, or a few berries make a clean garnish. Add fresh fruit close to serving time, since cut kiwi can release juice onto the frosting as it sits. Let refrigerated cupcakes stand for about 20 minutes before serving so the buttercream softens slightly.
Variations
Make it smoother: Strain the cooked puree through a fine-mesh sieve before cooling. This removes the small black seeds but does not change the flavor. If you like a little texture, skip straining; the seeds are edible and give the frosting a homemade, fruit-forward appearance.
Use golden kiwi: Substitute the same amount of peeled, diced golden kiwi. It is often sweeter and less tart than green kiwi, and the frosting will have a warmer, more yellow tone. Taste the puree before mixing it in, then use less powdered sugar only if the finished frosting remains firm and tastes balanced.
Add citrus: Beat in ½ teaspoon finely grated lime zest (about 1 g) with the vanilla for a brighter aroma. Avoid adding much lime juice: extra liquid can loosen the buttercream, and the kiwi already brings acidity. For a gently spiced version, add a pinch of ground ginger alongside the salt.
Make a dairy-free version: Use a firm plant-based butter stick intended for baking in place of dairy butter. Soft tub spreads contain more water and are likely to make the frosting loose. Choose a neutral-tasting product, and add the puree slowly because plant-based fats can behave differently from dairy butter.
Storage and Reheating
Because this frosting contains butter and fresh fruit puree, refrigerate it in an airtight container within 2 hours of making it. It keeps for 3–4 days in the refrigerator. A frosted cake or cupcakes should also be covered and refrigerated within 2 hours; in a room hotter than 90°F (32°C), refrigerate within 1 hour. Keep the frosting away from uncovered foods so it does not pick up refrigerator odors.
To freeze the frosting, pack it in a freezer-safe airtight container for up to 2 months. Thaw it overnight in the refrigerator, then let it sit at room temperature for about 20–30 minutes and beat it briefly until smooth. If it looks separated at first, keep beating for another minute before deciding whether it needs adjustment. Do not microwave it to soften it: warm spots can melt the butter and leave the frosting greasy. Reheating is not needed; this is a ready-to-use topping.
If you have leftover frosting on a serving plate, return it to the refrigerator promptly rather than leaving it out for an extended period. A short time at room temperature makes it easier to spread, but it should not sit out for more than 2 hours total, or more than 1 hour when the room is above 90°F (32°C). For best piping results, use it cool but pliable, not warm.
Frequently Asked Questions
Can I put raw kiwi straight into buttercream?
It is better to cook it first. Raw kiwi contains actinidin, an enzyme that breaks down proteins and can interfere with dairy-based mixtures over time. Fresh kiwi also adds a lot of water, which may make buttercream thin. Simmering the fruit reduces moisture and deactivates the enzyme, giving the frosting a more reliable texture.
Can I use frozen kiwi?
Yes. Thaw it in the refrigerator, drain away any liquid, and measure 1 cup (about 180 g) of the fruit before cooking. Frozen kiwi may be softer and release more water, so simmer it until the puree is thick and reduced to roughly ⅓ cup. Cool it completely before adding it to the buttercream, just as you would fresh fruit.
Why is my kiwi frosting runny?
The most common cause is puree that was not reduced enough or was added while warm. Chill the frosting for 15–20 minutes, then beat it briefly. If it is still too soft, add powdered sugar a tablespoon at a time. Next time, reduce the kiwi to a thick ⅓ cup and mix it in gradually, stopping as soon as the flavor and consistency are right.
Will it taste strongly of kiwi?
It has a gentle, tangy kiwi flavor rather than the intensity of a fruit jam. Using the full amount of cooled puree gives a more noticeable fruit note, while starting with 3 tablespoons keeps it milder. Taste as you go, since the sweetness and tartness of individual kiwis vary. The vanilla and butter soften the fruit’s sharper edges.
Can I make the frosting ahead?
Yes. Prepare it up to 3–4 days ahead and keep it covered in the refrigerator, or freeze it for up to 2 months. Before using, thaw frozen frosting overnight in the refrigerator, let it soften briefly at room temperature, and beat it again to restore a spreadable texture. Do not leave it out for hours to thaw.
Can I pipe kiwi frosting onto a cake?
Yes, provided it is thick enough to hold a peak. For defined piping, begin with less puree and add only enough to give the flavor you want. If the frosting feels soft, chill it for 15–20 minutes before filling a piping bag. A broad star or round tip is a practical choice; very delicate shapes may soften faster than plain swirls.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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