Lemon Curd Swiss Buttercream
Deliciously light in texture, with a beautiful lemon curd undertone. This Lemon curd Swiss meringue buttercream is perfect for frosting cakes and cupcakes!
Equipment
- Stand Mixer with Whisk and Paddle Attachment
Ingredients
Lemon Curd
- 3 large egg yolks save the egg whites for the buttercream
- 1 large whole egg
- 150 g granulated sugar
- 120 g fresh lemon juice
- 2 Tablespoons lemon zest
- 85 g unsalted butter cold
- 1/8 tsp salt
Swiss Meringue Buttercream
- 6 large egg whites
- 300 g granulated sugar
- 400 g unsalted butter room temperature
- All the lemon curd
- 1/8 tsp salt
Instructions
Lemon Curd
- In a microwave-proof bowl, whisk together the egg yolks, whole egg, and sugar until well combined. Whisk in the lemon juice and lemon zest. Save the egg whites for the meringue.
- Place the bowl in the microwave and cook in 40-second increments, stirring each time for around 3-4 minutes in total. This time may increase or decrease depending on your microwave strength.
- Dip a metal spoon in the curd to check that it is thick enough. The curd should easily coat the back of the spoon and be visibly thicker.
- Stir the cold cubed butter through the hot curd and stir until smooth. Pour the finished curd through a sieve into clean jars. It will thicken as it cools. Once cooled, store it in the fridge. Leave it to sit at room temperature for around 20-30 minutes before using so it's not too cold.
Buttercream
- Bring a medium saucepan with 1-2 inches of water to a simmer.
- Combine egg whites and granulated sugar in the metal bowl of a stand mixer or other heatproof bowl. Balance the bottom of the bowl over the simmering water bath, but ensure it’s not touching the water.
- Whisk continuously as the egg whites warm up, ensuring all the sugar has dissolved or the temperature reaches 160°F (71°C) on an instant-read thermometer.
- Once the sugar has dissolved, place the bowl in your stand mixer fitted with the whisk attachment.
- Beat on medium-high speed until the stiff peak stage and the meringue cools to room temperature.
- Add a few pieces of softened butter to the meringue base with the mixer still on medium-high speed. At this stage, the frosting may separate or curdle – don’t panic! Just continue beating the mixture until it becomes a thick and cohesive buttercream. This process can take time, so don’t give up if it seems slow – it will come together.
- Once the mixture is thick and cohesive, add the lemon curd and salt.
- Beat the buttercream until is thick and fluffy. See notes below for if it doesn't come together,
- Switch to the paddle attachment and beat on low for 10 minutes to knock out the larger air bubbles in the buttercream. Now it’s ready to start piping and frosting!
- Swiss meringue buttercream can be stored in a covered bowl at room temperature for 1-2 days, as long as the room doesn’t get too warm. If your kitchen is warm, store it in the fridge or freezer until needed, and follow the instructions in the notes to re-whip it.
Notes
This makes around 5 cups of buttercream. This is enough to fill a 2-layer 9-inch cake generously, or a 3-layer 8-inch cake, and ice 12-24 cupcakes, depending on how much frosting you like to use.
If your buttercream isn't coming together (whether curdled or soupy), don't panic! It's just a temperature thing and there's always a fix. It's just a matter of temperature so that the mixture emulsifies well.
Initially it’s common for the mixture to split as the butter is added, especially if the egg whites and butter aren’t at the same temperature. Just keep beating it until it comes together
Important notes
If the meringue or the butter is too warm. Then the butter will melt and make a soupy and runny texture. Solution: Chill the bowl briefly in the fridge then rewhip til smooth. If the butter is too cold. Then the mixture will appear curdled and lumpy. Solution: Keep whisking to remove this, but if it doesn't work, place the bowl over warm water for a little while to melt the edges, then whip again.Rewhipping cold Swiss meringue buttercream
As the buttercream cools in the refrigerator, it will become hard as all the butter there has solidified. Bring it back to room temperature and whip it to make it creamy. You can leave it to sit out and warm up for a few hours, or gently warm the buttercream bowl over a hot water bath until the buttercream edges in the bowl begin to melt. Once the edges have melted, place the bowl back in the stand mixer and whip it for 3-5 minutes until creamy again. If the mixture appears to split and become curdled, the butter is still too cold, and it will need a little more warming. If it becomes soupy and liquid it has warmed too much, so place it back in the fridge to cool it down. Whichever way it swings, there’s a fix for it, you need to get it at the right temperature.Nutrition
Serving: 1servingCalories: 398kcalCarbohydrates: 37gProtein: 3gFat: 28gSaturated Fat: 17gPolyunsaturated Fat: 1gMonounsaturated Fat: 7gTrans Fat: 1gCholesterol: 119mgSodium: 71mgPotassium: 48mgFiber: 0.1gSugar: 37gVitamin A: 876IUVitamin C: 4mgCalcium: 17mgIron: 0.2mg
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