Place the condensed milk in a sufficiently high pot. Cover with water and heat up. Let everything simmer for about 2 1/2 hours. The can must always be covered with water, top up with water if necessary. Take the tin out and let it cool down.
Melt the butter. Finely crumble the biscuits, mix with the butter. Put aside about 1 tbsp. for sprinkling. Divide the rest into 4 glasses (each containing approx. 350 ml) and press them slightly. Whip the cream until stiff and let the vanilla sugar trickle in. Spread some cream on the crumb mixture.
Open the tin and pour approx. 2/3 of the milk caramel onto the cream (use the remaining caramel for other purposes). Peel and slice the bananas and sprinkle with lemon juice. Spread the bananas and the remaining cream in the glasses. Sprinkle with cookie crumbs set aside and dust with cocoa.