In a medium bowl, combine sliced strawberries, 3 Tbsp of sugar and 4 Tbsp of Grand Marnier. Mix together. Cover and refrigerate 1 hour stirring occasionally.
In a separate bowl combine 1 cup of cold heavy whipping cream and 1/4 cup of powdered sugar. Beat with electric mixer until stiff peaks form. Using a spatula, fold in 1/4 cup of the sour cream until well blended.
Divide strawberries into 8 glass bowls or glasses. Top with whipped cream just before serving. This dessert is taste the best on the same day it is made. Enjoy!