• Bring all ingredients to room temperature. Verify the temperature with Thermapen® ONE.
• Whip the butter, salt, and vanilla in a stand mixer using the paddle attachment on medium speed for 3 minutes until light and fluffy.
• Add the lemon juice. Transfer to a medium bowl.
• Wash the stand mixer bowl and start whipping the whole egg and egg yolks using the whisk attachment on medium speed for 2 minutes.
• In the meantime, cook the water, sugar, and corn syrup to 250°F (121°C) in a small saucepan. (subtract 1°F for each 500ft elevation above sea level.)
• While whipping the egg mixture on medium speed, slowly pour in the sugar syrup near the side of the bowl.
• Then, whip on high speed for 3 minutes until the egg mixture is cooled to 104°F (40°C).
• While on low speed, add the butter mixture to the egg mixture and whisk until light and fluffy.
• Use immediately to fill and frost your cakes.

Note:

• Buttercream can also be stored in a refrigerator for up to three days or the freezer for up to one month.