1teaspoonwhite vinegar, or lemon juice, see Recipe Notes, optional
4large egg whites, at room temperature, see Recipe Notes
½teaspooncream of tartar
1½cupsbutter, at room temperature
flavorings, see Recipe Notes
food coloring, see Recipe Notes
Remove 1 tablespoon of sugar and set aside.
Wet a paper towel with white vinegar or lemon juice and wipe the bowl of a stand mixer. Place the egg whites in the bowl and fit the mixer with the whisk attachment.
In a small saucepan, combine the remaining sugar and water and stir. Place the pan over medium high heat and boil until it reaches firm-ball stage (248°F to 250°F).
When the sugar starts boiling, begin beating the egg whites on a medium speed until frothy. Sprinkle in the cream of tartar and the 1 tablespoon sugar. Increase speed to medium high and beat until stiff peaks form. Don’t overwhip or the meringue can start to separate. If it’s ready before the sugar is to temperature, turn the mixer to the lowest speed and let it continue to run.
When the syrup and meringue are ready, pour the hot syrup into the meringue in a thin, steady stream along the side of the bowl while the mixer is running. Continue beating until the bottom of the bowl feels cool to the touch, and is thick and glossy. The meringue needs to be completely cooled down before adding the butter.
With the mixer running at medium speed, add the butter 2 tablespoons at a time. Beat until each addition of the butter is mostly incorporated before adding more. The buttercream may start to look curdled, but it should smooth out. See the Recipe Notes for troubleshooting tips.
After all the butter has been fully incorporated, add the flavorings and or food colorings of your choice. Your Italian Meringue Buttercream is ready!
Egg whites need to be absolutely free of fat to whip into a meringue. To make sure there is no yolk, separate the eggs over a bowl and dump the whites into another bowl (an egg separator can help). Also, wiping the mixing bowl with white vinegar or lemon juice prior to adding the whites help to ensure there is no fat in the bowl that can inhibit the meringue formation. This step is optional but highly recommended.Do not stir the sugar while the mixture heats as that can cause the sugar to crystalize.You want to have the sugar syrup reach the right temperature as the meringue just comes to stiff peaks. If the syrup is done before the meringue is ready, add a very small amount of hot (not cold) water to lower the temperature slightly.Storing Buttercream: You can make the buttercream ahead of time and store it in the refrigerator for a week or freeze it for up to 2 months. Bring it to room temperature then beat to a smooth consistency before using. If it’s frozen, allow the buttercream to defrost overnight in the refrigerator before having it sit out on the counter.If you want to color your buttercream, gel food coloring works best.Troubleshooting Tips
If the buttercream looks curdled or runny, the butter has melted because the meringue is too warm. Place the mixing bowl in the refrigerator for about 15 to 20 minutes, then return to beating until the buttercream is smooth.
If the butter doesn’t mix well into the meringue, either the butter or the meringue are too cold. Hold a heating pad set to medium-high onto the bowl while beating. You can also use a hair dryer set to warm, blowing around the bottom of the bowl.
Flavor variations: Here is where you can get creative by adding these flavorings after all the butter is incorporated.