Buttercream frosting (yields frosting for a two layer 9-in. round cake)

4 large (200 g) eggs	whisk	whisk over double boiler until 160°F	beat on medium-high speed 5 min.	beat butter in on low speed	beat until smooth and silky
1 cup (200 g) granulated sugar
2 tsp. (10 mL) vanilla extract
1/2 tsp. (3 g) table salt
1 lb. (450 g) unsalted butter	cut into 16 to 20 pieces