Mash half of the strawberries in a large bowl. Add the sliced strawberries, sugar, Grand Marnier and mint and chill.
Beat the heavy cream into soft peaks, add the vanilla and sprinkle in the powdered sugar while mixing just a little more until you have stiff peaks but don't over beat it. If you over beat it (where is looks separated) you need to start over.
Slice the pound cake and place on plates, top with strawberries and whipped cream.