Ingredients:
- 1 lb (450 g) unsalted butter, cut into 1-inch cubes, at room temperature (around 68°F/20°C)
- 6 large egg whites (approx. 180 g)
- 1 ½ cups (300 g) granulated sugar (caster sugar)
- 2 tsp (10 mL) pure vanilla extract
- ¼ tsp (1.25 g) fine sea salt
Instructions:
- Set up the Bain-Marie: Fill a saucepan with about 1 inch (2.5 cm) of water and bring it to a simmer. Ensure the heatproof mixing bowl fits snugly on top without the water touching the bottom.
- Combine Ingredients: Place the egg whites and granulated sugar into the heatproof bowl. Whisk gently by hand until combined.
- Cook the Meringue: Place the bowl over the simmering water. Whisk continuously and vigorously until the sugar is completely dissolved and the mixture registers 160°F (71°C) on a digital thermometer.
- Remove from Heat: Immediately remove the bowl from the pan and wipe the bottom clean of any condensation to prevent water from dripping into the meringue.
- Whip the Meringue: Transfer the cooked egg mixture to the stand mixer bowl and attach the whisk. Begin whipping on low speed for 1 minute, then increase to medium-high (speed 8-10).
- Whip to Stiff Peaks: Continue whipping until the meringue forms stiff, glossy peaks. This process usually takes 8–12 minutes. Crucially, the bowl must cool down completely to ambient room temperature (below 80°F/27°C).
- Switch Attachments: Replace the whisk with the paddle attachment. Reduce the mixer speed to medium-low.
- Add Butter Gradually: Add the room temperature butter, one cube at a time, allowing each cube to be fully incorporated before adding the next. The mixture will look curdled like cottage cheese—do not panic.
- Emulsification: Continue beating at medium speed. After 3-5 minutes, the mixture will suddenly transform into a smooth, thick, and luxurious Swiss Meringue Buttercream.
- Final Flavours: Once smooth, stop the mixer. Scrape down the bowl. Add the vanilla extract and fine sea salt. Mix briefly on low speed until combined.