Preheat oven to 350; grease a 13x9 pan; set aside.
In a small bowl, combine crust ingredients; press into prepared pan; bake for 18-20 minutes (golden brown); cool.
In a large sauce pan, combine sugar & cornstarch; stir in rhubarb; bring to a boil (medium heat), stirring often; reduce heat, cook & stir for 4-5 more minutes -thickened; remove from heat, cool.
Stir in strawberries; set aside.
In a small mixing bowl, beat cream cheese and powdered sugar (smooth); fold in one cup of the WHIPPED cream; spread over crust; top with rhubarb-berry mixture; spread with with remaining whipped cream.
Chill for 3-4 hours before serving.
Garnish with a sprinkle of brown sugar if desired.