Preheat the oven to 180°C.
Melt the butter in a small saucepan over a low heat (or in the microwave). Remove from heat and add the milk chocolate. Stir until combined. Set the mixture aside until it reached room temperature.

In a bowl, whisk the eggs and sugar until combined and fluffy. Add the cold chocolate mixture and mix. Add the flour and salt and mix well. Finally, add the chocolate chips and stir in the mixture.

Transfer the mixture to a buttered and floured 20 cm baking tray; bake for 30 minutes, or until the brownie is set. Allow to cool for 20 minutes and serve.