Pre-heat the oven to 180C fan-forced and line two baking trays with baking paper.
Beat the butter, sugar and condensed milk together in the bowl of an electric mixer until pale and smooth.
Add the flour, chocolate chips and nuts and mix them through until there are no dry bits.
Roll tablespoon-sized balls of dough and place then on the trays leaving 5cm between each one.
Gently press the dough down to flatten it.
Bake for 10 minutes or until slightly golden.
Leave the biscuits on the trays for 5 minutes and then transfer to a wire rack to cool completely.