In shallow bowl, combine orange juice and orange liqueur (if using). 

In large bowl, using electric mixer, on medium speed, beat mascarpone, sugar and orange rind until creamy. In medium bowl, with clean beaters, beat whipping cream with vanilla until soft peaks hold. Fold half of the cream into mascarpone mixture; fold in remaining cream.

Slice about half the strawberries. Reserve remaining strawberries. Quickly dip both sides of biscuits into juice mixture; arrange in single layer, covering bottom of 8- x 8-inch (2 L) glass baking dish, breaking to fit if needed. Spoon half of the mascarpone mixture over ladyfingers, spreading to edges. Scatter sliced strawberries on top in even layer; sprinkle with half of the grated chocolate. Repeat layering with remaining biscuits, drizzling any extra orange juice mixture over top. Spread remaining mascarpone mixture over biscuits. Refrigerate loosely covered 8 hours or overnight.

To serve, quarter or halve the remaining strawberries, scatter over tiramisu. Sprinkle with remaining chocolate. Cut in rectangles and serve.