Grease a 9x13 inch baking pan (bottom and sides) set aside.
In a microwave safe bowl, combine margarine, marshmallows, and cocoa powder. Heat on HIGH until melted (about 1 minute) stir to combine. Stir in vanilla extract.
Add crushed Shreddies to marshmallow mixture one cup at a time. Stir to combine and coat all the Shreddies (if too sticky add more crushed shreddies accordingly). Pour mixture into greased pan, press down firmly.
Layer strawberries and bananas on top.
For the topping heat white chocolate chips with 2 teaspoons margarine in the microwave until melted (about 40 seconds). Stir to combine.
Generously drizzle melted white chocolate over your chocolate Shreddies banana and strawberry bars. Let set and chill for 40 minutes.
Cut into bars and enjoy!
Makes between 18-24 bars (depending on how big you cut them!).