Light and Fluffy Italian Buttercream

Italian buttercream is meringue-based. "Italian meringue is prepared by the addition of sugar syrup made by heating sugar and water (and sometimes the addition of glucose or corn syrup to stabilize the crystal structure) heated to the soft-ball stage (118°C, 240 °F) to egg whites whipped to soft peaks. The sugar syrup cooks the egg whites, heating them well past the 60°C (140°F) recommended in the USA to kill salmonella and any other potentially harmful bacteria. The syrup and egg white mixture is then whipped and cooled until it reaches room temperature. Buttercream prepared in this method is also often referred to as Mousseline buttercream." - Wikipedia 

Italian buttercream is my preferred frosting for cakes and cupcakes. The following recipe is the best that I've used and is found in the CIA textbook Baking and Pastry: Mastering the Art and Craft. The addition of sea salt and notes in [ ] are from my experience and not in the original recipe.

Makes 3 lb 4 oz (1.47 kg) - [mixes well in a 6-qt bowl of a stand mixer]

Ingredients

  • 1 lb (454 g)  granulated sugar
  • 4 fl oz (120 ml)  water
  • 8 oz (227 g)  egg whites [at room temperature]
  • 2 lb (907 g)  unsalted butter, cut into medium chunks, soft
  • 1 tsp  sea salt
  • 1 T (15 ml)  vanilla extract [or vanilla bean paste]

Directions

  1. Combine 12 oz/340 g of the sugar with the water in a heavy-bottomed saucepan and bring to a boil over medium-high heat, stirring to dissolve the sugar.  Continue cooking, without stirring, to the soft ball stage (240 degrees F/116 degrees C).
  2. Meanwhile, place the egg whites in the bowl of an electric mixer fitted with the wire whip attachment.
  3. When the sugar syrup has reached approximately 230 degrees F/110 degrees C, whip the egg whites on medium speed until frothy.  Gradually add the remaining 4 oz/113 g sugar [and sea salt] and beat the meringue to medium peaks.
  4. When the sugar syrup reaches 240 degrees F/116 degrees C, add it to the meringue in a slow, steady stream while whipping on medium speed.  Whip on high speed until the meringue has cooled to room temperature.
  5. Add the soft butter gradually, mixing until fully incorporated after each addition and scraping down the sides of the bowl as necessary.  Blend in the vanilla [or vanilla bean paste].  The buttercream is ready for use or may be tightly covered and stored under refrigeration. [Double wrapping in plastic film is the easiest and best way to store your buttercream. And double wrapping prevents food odors from seeping into your frosting. An off tasting buttercream is not good eats.]