Pour the white chocolate pieces into a microwave safe dish.
Heat on the defrost setting for one minute.
Let the chocolate sit for 2 to 3 minutes.
Stir until smooth and no clumps remain, heating an additional 15 seconds if needed. Set aside.
Place the butter into the bowl of an electric mixer fitted with the paddle attachment.
Beat at low speed for 2 minutes, or until the butter has been whipped well.
Scrape the sides of the bowl with a spatula.
Add the melted white chocolate and continue to mix on low speed until fully combined, about 1 minute.
Scrape the sides of the bowl and add the powdered sugar, one cup at a time, along with the salt.
Stir in the heavy cream and vanilla.
Turn the speed of the mixer to medium and allow the frosting to mix for 5 minutes, scraping once halfway through.
Spread or pipe onto your cooled cupcakes.