Line a 9×9-inch square pan with aluminum foil. Set aside.
Place the chocolate and butter in a heat-proof bowl. Melt together over a pot of barely simmering water or in the microwave, taking care not to overheat the ingredients. Stir until you have a smooth consistency. Add the peanut butter and condensed milk and continue stirring until smooth. Using a spatula, gently fold in the cereal and once evenly combined, transfer to your prepared pan. Smooth the top so you have an even surface. Set aside.
For the topping, melt the chocolate, again you can do it over a pot of simmering water or in the microwave. Once melted and smooth, pour into your prepared pan and spread out with a spatula to ensure you have an even layer of chocolate. Warm the 1/4 cup peanut butter in a small bowl in the microwave. You want the peanut butter to be the right consistency for drizzling. Using a piping bag or large spoon, drizzle the runny peanut butter on top of your melted chocolate.
Transfer the pan to the fridge and leave to set for at least two hours.