6 large egg whites
2 cups granulated sugar
1 and 1/2 cups unsalted butter, softened (For better results use Kerry Gold butter)
2 teaspoons pure vanilla extract
Pinch of salt
Separate 1 egg white in a small bowl, then place the egg white in your heat proof mixing bowl. Repeat with the remaining egg whites
Whisk sugar into the egg whites, then set the bowl over a saucepan filled with just two inches of simmering water over medium heat. Whisk the whites and sugar constantly until sugar is dissolved and mixture has thinned out, about 4 minutes.
The mixture will be thick and tacky at first, then thin out and be frothy white on top. To test that it’s ready, you can use your finger or an instant read thermometer. Grab a spoon, dip it in the mixture and touch the back of the spoon and rub the mixture between your thumb and finger. You shouldn’t feel any sugar granules. If using a thermometer, the temperature should read 160°F (71°C).
Transfer mixture to the bowl of a stand mixer fitted with a whisk attachment. On medium-high speed, beat the mixture until stiff glossy peaks form and the meringue is no longer warm to the touch, at least 10-15 minutes.
If the bowl and meringue still feel warm, wait until both cool to room temperature before adding the butter in the next step. Feel free to place it in the refrigerator. A warm bowl and meringue will melt the butter.
Switch the stand mixer to the paddle attachment. On medium-high speed, add the butter 1 Tablespoon at a time. Wait for the butter to fully mix in before adding the next Tablespoon. After all the butter has been added, turn the mixer down to medium speed and fully beat in the vanilla and salt, about 30 seconds.