Coarsely chop the white chocolate baking squares.

Combine chopped white chocolate and 2/3 cup heavy cream in a heavy saucepan.

Heat over medium-low heat, stirring constantly.

Continue cooking and stirring until the chocolate is completely melted and the mixture is smooth.

Remove from heat and cool to room temperature.

In a separate small mixing bowl, pour the remaining heavy cream.

Add confectioners' sugar and vanilla extract to the cream.

Beat with a mixer until soft peaks form.

Gently fold about 1/4 cup of the whipped cream into the cooled chocolate mixture to temper it.

Gently fold in the remaining whipped cream mixture until just combined, being careful not to deflate the cream.

Spoon the mousse mixture evenly into individual dessert dishes or glasses.

Cover each dish with plastic wrap or a lid to prevent a skin from forming.

Refrigerate for at least two hours, or until the mousse is set.