Line a 13 or 14 inch pizza stone (or pan) with parchment paper (I like to trace the stone and cut it out).
Whisk egg, oil, and water together in a large bowl and then mix in the brownie mix until combined.
Pour batter onto the middle of the parchment covered stone (pan). Spread evenly into ~11 inch circle or at least 1 inch away from the edges. Place in oven and bake 18-20 minutes until set. Allow the brownie to cool completely.
With an electric mixer, beat cream cheese, sugar, and vanilla until smooth. Add the whipping cream and beat until stiff peaks. Scrape down sides of bowl as needed. Stir in the chopped strawberries and spread mixture over the cooled brownies.
Decorate with sliced strawberries, raspberries, and blueberries. (Optional- brush berries with seedless jam for a glossy look.) Sprinkle chocolate over the top of the berries.
Chill until ready to serve and then cut into wedges or squares.
*You can substitute the heavy cream for cool whip. Only use 1 tablespoon granulated sugar if you make this substitution.