This is the one I reach for most in a professional kitchen. It's built the same way as Swiss meringue buttercream, but the hot-syrup method makes it noticeably more stable — which matters a lot on a warm event day.
Italian meringue buttercream and Swiss meringue buttercream get compared constantly, and honestly, they taste and behave very similarly once they're finished. The difference is in the method: instead of gently heating egg whites and sugar together, you cook the sugar into a syrup separately and stream it into whipping egg whites. That extra step buys you two things — a more stable finished buttercream that holds up better in a warm room, and a meringue with noticeably fewer air bubbles.
The part that takes practice: streaming the syrup
The syrup needs to hit exactly 240°F / 115°C before it goes in — pull it too early and the buttercream will be loose; too late and it can seize into hard sugar threads. Once it's at temperature, pour it in a thin, steady stream aimed at the space between the whisk and the side of the bowl, never directly onto the moving whisk (it'll fling hot sugar) and never straight onto the bowl's side (it can harden there instead of incorporating).
Why this one holds up better: cooking the sugar to a higher temperature and folding it into an already-whipping meringue produces a denser, more stable protein structure than gently warming egg whites and sugar together. That's the whole reason professional cake decorators lean on Italian meringue buttercream for outdoor events, wedding cakes, and anything that has to survive a few hours out of the fridge.
Combine sugar and water in a pot over medium-low heat. Use a candy thermometer.
Have egg whites ready in a stand mixer with the whisk attachment.
At 200°F / 93°C, start whisking the whites on medium-high until they're filling with air.
At 240°F / 115°C, remove syrup from heat and stream it into the whisking egg whites, avoiding the sides of the bowl.
Continue mixing 8–10 minutes until completely cool and at stiff peaks.
Add vanilla and salt.
Add the butter one cube at a time. It will look curdled — keep mixing until smooth and silky.
Notes: More stable than Swiss meringue buttercream in warm environments, with fewer air bubbles. Pipes cleanly and smooths beautifully. Refrigerate up to a week; bring to room temperature and re-whip before using.
by Alejandro, PastryPath · Updated July 2026
