Grease and line a 1.25L loaf pan with plastic wrap, leaving plenty overhanging.
Place chocolate and biscuits in a food processor and whiz until coarse crumbs. Add butter and whiz to combine.
Press half the crumbs into base of the pan, then spoon over half the ice-cream. Place dulce de leche in a piping bag fitted with a 2cm nozzle, then pipe an even layer over ice-cream. Top with remaining ice-cream, followed by remaining crumbs, then cover with plastic wrap. Top with a piece of cardboard cut to fit and weigh with cans. Freeze for 2 hours or until frozen, then invert onto a plate and serve.