Line a 9x9" baking tray with parchment paper. Set aside.

Melt the initial 120g chocolate. 

To a medium saucepan, add the vegan condensed milk, melted vegan butter and melted chocolate. Mix for roughly 5 minutes over a medium-high heat. It should become thick and runny like ordinary caramel. Cook for a further minute or so if you'd like it even thicker.

Pour the puffed rice into a medium bowl.  Then pour over the caramel sauce until the puffed rice is fully covered, sticky and brown. Press it firmly into the base of the prepared baking tin. I used the bottom of a glass. 

Place the caramel puffed rice base into the refrigerator for 30 minutes to set. 

Once the base is almost set, melt the remaining 450g chocolate using the double boiling method. You can also melt it another way but I find double boiling the best for not burning the chocolate.

 Pour the chocolate over the base and allow it to set at room temperature. I also added vegan sprinkles. As soon as the topping has hardened, serve.