Brush a 20 x 30cm (base measurement) rectangular cake pan with melted butter. Line the base and 2 long sides with non-stick baking paper, allowing the sides to overhang. Combine the rice bubbles and granola in a large bowl.
Whisk the condensed milk, butter and honey in a small saucepan over low heat until the butter melts. Simmer, whisking constantly, for 10 minutes or until the mixture turns into pale caramel. Make a well in the centre of the cereal mixture. Pour in the hot caramel. Stir until well combined.
Use the back of a metal spoon to press the mixture firmly over the base of the lined pan. Sprinkle with the choc bits and use your hands to gently press into the granola mixture. Place in the fridge for 6 hours or overnight to set.
Use the overhanging paper to lift the slice from the pan. Cut into bars. Store in an airtight container for up to a week.