Using a clean towel and some lemon juice or vinegar, clean your mixing bowl, whisk attachment to remove any traces of grease.
Fill a heavy duty pot about a quarter of the way with water and place on the stove over medium heat to simmer.
Add egg whites, sugar and salt to the mixing bowl and whisk together lightly with a hand whisk, just until combined. Fit the bowl onto the pot, ensuring the bottom of the bowl is not in contact with the water in the pot. Whisk the sugar egg white mixture constantly, but gently, until temperature reaches 160°F.
Once at the correct temperature, remove carefully from heat, wipe the moisture away from the bottom of the bowl and transfer mixing bowl to the stand mixer. With the whisk attachment, begin to whip the meringue until it is thick, glossy, and the bottom of the bowl is no longer warm to the touch. Do not begin adding butter while the bowl is still warm.
Switch from your whisk to paddle attachment and with mixer on low speed, add butter cubes, one at a time, until incorporated. Continue to mix until it has reached a silky smooth texture.
Add vanilla beans and Amarula liqueur, continuing to beat on low speed until well combined.