Place chocolate, condensed milk and butter into slow cooker on high with the lid off. Stir with a metal or silicon spoon every 15 minutes until melted and turn setting down to low and continue to stir every 15 mins for up to 2 hours.
Pour into a lined 20cm x 20 cm square cake tin and smooth over the top.
Sprinkle with M&M’s Mini and place into the fridge to cool for 1 hour. Cut into squares and serve.
