Preheat your oven to 350°F (175°C).
Line a 9x9-inch baking pan with parchment paper, leaving some overhang for easy removal.
In a medium saucepan over low heat, melt the butter and chopped white chocolate together. Stir until smooth and fully combined. Remove from heat and let it cool slightly.
In a large mixing bowl, whisk together the eggs and granulated sugar until pale and fluffy. Add in the vanilla extract and mix well.
Pour the melted butter and white chocolate mixture into the egg and sugar mixture. Stir until well combined. Sift in the all-purpose flour and salt, mixing slowly until just incorporated.
Gently fold in the chopped macadamia nuts and milk chocolate chips.
Pour the brownie batter into the prepared baking pan and spread it evenly. Bake for about 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan for at least 15 minutes before lifting them out using the parchment paper. Once fully cooled, cut into squares and serve.