Ingredients:
- 5 large (150 g) egg whites
- 1 cup (200 g) granulated sugar
- 1/8 tsp (1 g) fine sea salt
- 1 cup (2 sticks / 225 g) unsalted butter, cut into 1-inch cubes, soft room temperature
- 1 tsp (5 mL) pure vanilla extract
Instructions:
- Set up the Bain-Marie: Fill a small saucepan with about 1 inch (2.5 cm) of water and bring to a simmer over medium-low heat. Ensure the water does not touch the bottom of the heatproof mixing bowl.
- Combine Ingredients: Place the egg whites, sugar, and salt into the heatproof bowl. Whisk lightly by hand until just combined.
- Heat Gently: Place the bowl over the simmering water. Whisk continuously for 5-8 minutes until the mixture reaches 160°F (71°C). The sugar grains should be completely dissolved.
- Whip to Stiff Peaks: Immediately attach the hot bowl to the stand mixer, fitted with the whisk attachment. Whip on medium speed for 2 minutes, then increase to medium-high until the meringue forms stiff, glossy peaks.
- Cool Completely: Continue whipping until the outside of the bowl feels completely cool to the touch (ideally below 80°F / 26°C). This cooling process may take 10-15 minutes.
- Switch Attachments: Change the attachment from the Whisk to the Paddle. Reduce the speed to low-medium.
- Add Butter Slowly: Add the soft, cubed butter, one cube at a time, allowing each cube to incorporate mostly before adding the next.
- Whip to Smoothness: The mixture will likely look curdled or soupy initially (the 'ugly phase'). Continue mixing on medium speed. After 5-10 minutes, the Swiss Meringue Buttercream will suddenly transform into a thick, pale, smooth, and velvety texture. Scrape down the bowl periodically.
- Final Flavouring: Once smooth, reduce speed to low and mix in the vanilla extract. Beat for one final minute to ensure everything is fully emulsified. Use immediately or store.