Spray a baking dish with non-stick spray. and set aside.
Combine the cake mix, water, oil, eggs and sour cream. Beat on low speed until mixed, and on medium speed for 1 minute.
Add the cup of chopped strawberries and mix by hand gently, until just combined.
Pour the batter into the prepared baking dish. Bake for ~27 minutes, or until toothpick inserted in center comes out clean.
Let the cake cool completely before frosting.
For the frosting: Beat the cream cheese and butter together in a large bowl until creamy. Slowly add the icing sugar until combined. Add the milk and vanilla. Beat on medium speed until frosting is smooth and free of any lumps.
Frost the cake, and add sliced or whole strawberries as topping.