Melt the white chocolate using a double boiler on low heat.
Make sure the water does not come in contact with the top portion of the double-boiler even after it starts to boil.
Stir the white chocolate continuously until it melts.
Remove the white chocolate from the heat after most of it has melted but a few lumps are still present.
The chocolate will continue to melt after being removed from the heat as long as you continue to stir it.
Let it cool.
In a stand mixer whip the butter for about 5 minutes over medium-high speed until pale, light and fluffy. Scrap the bowl once or twice during that time.
Start adding cream cheese beating until light and fluffy again.
Stop the mixer and scrape the sides and, the bottom of the bowl, with a silicone spatula, then add the melted and completely cooled white chocolate and vanilla and mix for 2-3 more minutes, or until fluffy.
Add little by little the add the sifted powdered sugar at a slow speed and mix until incorporated and creamy, scrap the sides and increase to medium-high speed again for about 2-3 minutes.
If you add the white chocolate not completely cool, the frosting will get thinner but you can leave it for a few minutes in the fridge or until you are ready to frost the cupcakes, and will stiffen again.
Frost your cupcakes and sprinkle a few Reese’s Peanut butter Chips on top.
Serve and enjoy!