To make the strawberry sauce, put all of the ingredients (except for the liqueur) in a saucepan.

Simmer on low heat for about 5 minutes (until the strawberries have released some of their juices and are still mostly intact). 

Allow the sauce to cool. 

Add the liqueur. Stir. Refrigerate until you are ready to assemble the cake.

Whip whipping cream for a minute on low speed. Add 3 tbsp of icing sugar. Whip for another minute. Pour the whipped cream into another bowl. Set aside.

Add the mascarpone to the bowl. Add the Gran Marnier, vanilla and icing sugar. Whip for a couple of minutes or until the mascarpone is soft. 

Fold the whipping cream into the whipped mascarpone until combined. Put mixture in the refrigerator until you're ready to assemble the cake.

Put parchment paper on the bottom of the springform pan. Cut in the shape of a circle. 

Cut the bottoms of the lady fingers so that they have a flat bottom and will stand up straight against the sides of the springform pan.

Arrange the lady fingers around the spring form pan.

Cover the bottom of the spring form pan with lady finger pieces. 

Cover the lady finger pieces with a little strawberry sauce. Try to keep the sauce away from the edges for this layer so that it doesn't seep out of the bottom of the pan.

Add a mascarpone cream layer.

Add another layer of the lady finger pieces.

Add a generous layer of strawberry sauce.

Add more mascarpone cream. 

Add fresh strawberries to decorate the top of the cake.