Fluffy Italian meringue buttercream made vegan! This frosting isn't too sweet and has an amazing buttery vanilla flavor. Perfect for frosting vegan cupcakes, sheet cakes. and layer cakes.
Start by reducing the aquafaba, add it to a saucepan and bring to a boil. Reduce the heat and allow it to simmer until it has reduced to half a cup in volume. After 5 minutes of simmering, check the volume by pouring the liquid into a measuring cup. If there's more than half a cup of liquid continue to simmer until it reduces to the required half cup.
Pour the reduced aquafaba into a jar and refrigerate. This can be done the night before or at least one hour in advance of making the recipe.
Add 200g of the caster sugar and water to a saucepan, gently stir and allow the mixture to sit for a minute until the sugar dissolves into a paste.
Place the saucepan on medium-high heat and allow the mixture to come to a simmer and bubble. DO NOT STIR throughout the entire process. Place your candy thermometer into the syrup and continue to simmer until the mixture reaches 116°C (240°F) - about 10-12 minutes.
Meanwhile, prepare the aquafaba. Take a large clean bowl, and make sure it's completely dry and free of any grease. Add the aquafaba and cream of tartar to a large bowl and whisk on high speed for 5 minutes until soft peaks form.
Slowly add in the remaining 50g of caster sugar, one dash at a time while continuing to whisk and incorporate the sugar into the aquafaba. Continue whisking for another 3 minutes.
Once the sugar syrup has reached the correct temperature begin to add it to the whipped aquafaba. Slowly drizzle in a little at a time and continue to whisk until the mixture is incorporated.
Whisk the meringue mixture for another 10-15 minutes until it has cooled to room temperature.
Start slowly adding the chunks of butter to the meringue, one at a time, allowing the mixture to incorporate for about 5 seconds between each one. The mixture will flatten as you add the butter, just continue to add the butter as it will stiffen when the full amount of butter is incorporated.
Once all the butter has been added the mixture be thick like buttercream, continue to whisk on low for 5 minutes.
Add the vanilla extract and whisk again on low for another 2 minutes.
Storage
You can store this Italian meringue buttercream in an airtight container in the fridge. It will harden when chilled, so before use, allow it to come to room temperature until it comes back to a creamy consistency.
Notes
Aquafaba: drain 1-2 cans of unsalted chickpeas, use only the liquid part.
I highly recommend using a candy thermometer. However, if you can’t wait to get one you can do something that’s called a softball test, you can read more about it on cooksinfo.com.
If your buttercream looks split even after adding all of the vegan butter to it, this can often be fixed by adding a little more butter.