In the bowl of a stand mixer fitted with the paddle attachment, beat cream cheese at medium speed until smooth, about 1 minute. Add sugar, and beat at medium-low speed until sugar is melted and mixture is smooth, stopping to scrape sides of bowl. Add melted white chocolate, and beat until well combined. With mixer on medium-low speed, add cold cream in a slow, steady stream. Thoroughly scrape sides of bowl. Slowly increase mixer speed to medium, beating until stiff peaks form, about 1 minute.