Chop rice cakes and set 1 cup (250 mL) aside.
In medium bowl, combine strawberries, liqueur (if using) and sugar. Transfer half to blender or food processor; puree until smooth. Return to remaining berries and mix to blend. Let stand at room temperature for 20 minutes. (Make-ahead: Can be refrigerated in airtight container for up to 24 hours.)
In large bowl, combine yogurt, pureed strawberries, orange liqueur, and chopped rice cakes. Spoon into 9-inch (23 cm) springform pan, smoothing top; sprinkle with remaining rice cakes. Cover and freeze until firm, about 4 hours. (Make-ahead: Overwrap in heavy-duty foil and freeze for up to 3 days.)
To serve, remove side of pan; slice cake into wedges. Garnish each with strawberry half and drizzle with strawberry sauce.