Mix graham cracker crumbs with softened butter and press mixture into 9-inch pie plate. Bake for 5 to 8 minutes.
Lower the oven to 300 degrees F for the toffee filling.
To create toffee filling, caramelize the sweetened condensed milk. Pour the condensed milk into a 9 by 12 by 2-inch glass baking dish. Cover with foil and place dish inside a larger poaching pan. Add water to poaching pan until half way up sides of baking dish. Bake for 1 1/2 hours.
Once both the crust and toffee filling are cooled, spread half of the filling evenly inside crust. Slice the bananas and layer on top of filling. Pour remaining half of filling over bananas, spreading evenly. Whip the cream with the confectioners' sugar and vanilla and spread on top of toffee filling and bananas.