Makes enough to frost and fill two 13-cm (5-inch) cakes, or one large 20-cm (8-inch) cake.
Ingredients
60ml (or ¼ cup) water
280g (or 1⅓ cup + 1 tablespoon) granulated sugar
4 large egg whites
1½ teaspoons vanilla extract
435g (or 1¾ cup + 2 tablespoons + 2 teaspoons) unsalted butter, cubed and at room temperature
3 tablespoons homemade or store bought orange curd
a few drop of orange food coloring
Instructions
In a small saucepan over medium heat, combine the sugar and water. Stir until the sugar has dissolved, then stop stirring. Pop in a candy thermometer and cook the syrup until it reaches 120°C or 248°F.
In the meantime, using a mixer fitted with the whisk attachment, whisk the egg whites until soft peaks form. When the syrup reaches the desired temperature, take the pan off the heat and, mixing gently, slowly drizzle in the hot syrup away from the whisk. Be careful: the sugar syrup obviously is very hot, and if you were to pour it onto the whisk it might splatter, so pour it down the side of the bowl instead.
Once all the syrup has been added, mix on high until the mixture is glossy and glorious and the meringue has cooled to body temperature. Keep mixing and start adding the softened butter, cube by cube, until all the butter has been added and the buttercream is gorgeously smooth and thick. Mix in the vanilla and the orange curd.
NOTE: the buttercream may look like it's curdling at some point. Don't worry about it and just keep mixing until it's smooth and fluffy.
Use at room temperature. Can be stored in the fridge, tightly covered with plastic wrap, for up to 1 week.
Recipe by The Tough Cookie at https://thetoughcookie.com/building-blocks-2/orange-swiss-buttercream/