Maple Buttercream Frosting

In a 3-quart stainless steel saucier, bring maple syrup to a boil over high heat. This should take no more than 5 minutes. If the timing is substantially different, this is simply an indication that the heat needs adjustment due to equipment variation.

Once the syrup begins to boil, reduce heat to medium and continue cooking until syrup reaches 230°F (110°C) on a clip-on digital thermometer, about 4 minutes longer (see note). Meanwhile, add egg whites to the bowl of a stand mixer fitted with a whisk attachment and begin whipping on medium-high speed.

Continue cooking maple syrup until it reaches between 240 and 250°F (116 and 121°C), about 3 minutes longer, adjusting the heat as needed and using a heat-resistant spatula to knock back the foam. When the syrup comes to temperature, remove from heat and pour into the bowl of egg whites in a steady stream, with the mixer still running. Take care that the syrup drizzles down the side of the bowl, so it does not come in contact with the moving whisk.

Once all of the syrup has been added, continue whipping the meringue until incredibly thick and glossy and cooled to approximately 85 to 90°F (29 to 32°C), about 4 minutes.

Add salt, followed by the butter in roughly 2-tablespoon increments, waiting only a few seconds after each one before adding the next. As the butter is added, the meringue will begin to deflate dramatically; this is normal. When all the butter has been added, reduce speed to medium-low and add vanilla, then shut off the mixer and scrape the bowl and beater with a flexible spatula. Re-whip a few seconds more; if problems arise, consult the troubleshooting guide below. Use immediately or transfer to an airtight container.