1. Prepare Your Ingredients and Equipment

• Measure everything beforehand to ensure smooth execution. Precision is key.
• Make sure your mixing bowl is clean and free of any fat or grease, as even a small amount can prevent the egg whites from whipping properly.

2. Whip the Egg Whites

• Begin by whipping the egg whites to stiff peaks. Ideally, they should reach stiff peaks at the same time your sugar syrup reaches the correct temperature (235°F). If your egg whites are whipping too fast, reduce the mixer speed to medium. Keep the egg whites moving but not overwhipping.

3. Cook the Sugar Syrup

• While the egg whites are whipping, heat the sugar and water to the soft ball stage (235°F / 113°C). Use a candy thermometer to monitor the temperature, or use the classic test: drop a small bit of syrup into ice water, and if it forms a malleable ball, it’s ready.
• Be careful not to overcook the sugar, as this can result in hard sugar lumps in your buttercream.

4. Combine the Syrup and Egg Whites

• With your mixer on high speed, slowly and carefully pour the sugar syrup down the side of the mixing bowl. Avoid hitting the whisk, as this could cause the hot syrup to splash or solidify on the whisk instead of mixing into the meringue.
• Keep mixing until the meringue forms stiff peaks and has cooled to just slightly warm. If the meringue is too hot when you add the butter, it will melt and ruin the texture.

5. Add the Butter

• Switch to the paddle attachment and begin adding the butter, one piece at a time. The butter should be soft but slightly cool. Squeeze each piece between your fingers to soften further before adding.
• Continue mixing until the butter is fully incorporated and the buttercream becomes smooth and creamy. If it looks lumpy or curdled, keep mixing—it will come together!

6. Whip Until Fluffy

• Once the butter is fully incorporated, switch back to the whisk attachment and whip the buttercream until it’s light and fluffy. This is also the time to add any desired flavorings (such as vanilla, almond extract, or fruit purées).