Cut the white chocolate into small pieces and melt in the top bowl of a double boiler over simmering water. Cutting the chocolate into small pieces ensures the chocolate will melt quickly and will decrease the chances of scorching the white chocolate. Stir frequently until chocolate is melted, then remove the bowl from the double boiler and set aside to cool.
Beat cream cheese and butter together using the paddle attachment in a stand mixer. You can also use a large bowl with a hand mixer. Beat ingredients for approximately one minute at medium speed until smooth and evenly incorporated. Scrape down sides of bowl to ensure all cream cheese is incorporated.
Add the slightly cooled white chocolate and stir on low speed until combined. If the white chocolate is too hot, it can melt the butter and change the consistency of the frosting.
Next, add the lemon juice and vanilla extract and stir to combine. While the mixer is on low speed, add the sifted powdered sugar in 2-3 additions so it doesn’t end up all over your kitchen.
Increase the mixer speed to high and beat until smooth and creamy.