In a bowl, melt your butter. Add in the sugars and stir until dissolved.
Stir in the egg, salt and vanilla until just combined.
Sieve in the flour, again stirring until just combined.
Stir in 190g of the chocolate chips.
Pour the batter into your lined tin and flatten until smooth. Drop your remaining chips on top. Chill in the fridge for 20=30 minutes.
Bake at 170C for 30 minutes. The texture of these bars should be semi cooked. Best eaten warm.