Combine first 3 ingredients, stirring well. Press into bottom of a 10-inch springform pan; freeze 15 minutes or until firm. Spread raspberry sorbet over crumb mixture. Freeze 1 hour. Spread lemon sorbet over raspberry sorbet. Cover and freeze 1 hour.
To serve, remove pie from pan. Arrange raspberries over lemon sorbet. Drizzle white chocolate over raspberries; slice pie into wedges. Garnish with mint sprigs, if desired.