Vanilla Buttercream Macaron Filling
- 4 oz. (½ cup) unsalted butter, at room temperature, cut into 4 to 6 pieces
- 2 large egg whites
- ½ cup granulated sugar
- ¼ tsp. pure vanilla extract
- Pinch of kosher salt
In a small heatproof bowl, whisk the sugar and egg whites. In a 1-quart saucepan, bring 2 cups of water to a simmer over medium-high heat. Set the bowl over the simmering water (don’t let the bowl touch the water) and heat the mixture, whisking occasionally, until hot to the touch, 4 to 6 minutes...