Put the white chocolate and ¼ cup heavy cream in a medium microwave-safe bowl. Microwave in 30-second intervals, stirring, until the chocolate is melted; whisk until smooth and creamy.

Beat the remaining 1 ¾ cups heavy cream in a large bowl with a whisk or mixer on medium-high speed until soft peaks form. Add the confectioners' sugar and vanilla; beat until hard peaks form, about 2 more minutes.

Whisk about 1 cup of the whipped cream into the chocolate mixture, then fold in the rest until combined.

Divide the mousse between serving cups and top with desired toppings.

Refrigerate until cold, at least 30 minutes.