In a food processor, add the cookies and process until it becomes a crumb-like mixture. Add the butter and process again. Set aside.
Meanwhile, take the condensed milk can and place it in an ovenproof stockpot filled with water. DO NOT OPEN THE CAN. Make sure the can is constantly covered in water. Bake in the oven for 3 1/2 hours. Remove, let cool, open and set aside.
In a bowl, mix the bananas with lemon juice. Set aside.
Whip the cream with icing sugar and coffee in another bowl until soft peaks form.
Using a round 4-inch mold directly on the serving plate, put a layer of the cookie mixture, then the slices of bananas, cover with the baked condensed milk (now toffee) and repeat the layers. Remove the mold and garnish with a dollop of cream.