Place butter, brown sugar and caster sugar into the bowl of a stand mixer fitted with a paddle attachment and whip on high speed until pale and creamy.
Add the eggs to the butter mixture one at a time and mix well in-between each addition. Once the eggs are incorporated add the chocolate bits and mix briefly to combine.
Remove the bowl from the mixer and fold through the salt and flour until a soft dough is formed.
Lay out a sheet of cling film and scoop out mounds of dough onto the cling film and roll the dough into a sausage shape. Place the dough into the fridge to rest for 40 minutes.
Line 2 baking trays with baking paper.
Once rested remove the dough from the cling film and cut it into 2cm thick pieces. Roll each piece of dough into a ball and place on the baking trays leaving some room in-between each cookie.
Place the trays in a pre-heated oven combi setting 190 °C for 15-18 minutes until golden.
Once baked remove the trays from the oven and leave to cool slightly.
Keep the cookies in a sealed container for 2-3 days or eat straight away with a cold glass of milk.