Melt the unsalted butter and dark chocolate together. You can do this by placing them in a heatproof bowl and setting it over a pan of simmering water. Stir occasionally until they are completely melted and well combined.

In a separate bowl, whisk together the eggs and golden caster sugar until they become thick and creamy. This whisking process helps to create the perfect texture for the brownies.

Next, combine the melted chocolate and butter mixture with the whisked eggs and sugar. Gently fold the ingredients together using a spatula or wooden spoon until they are fully incorporated.

Now it's time to add the extra bursts of chocolatey goodness. Fold in the white and milk chocolate chunks into the batter. This will create pockets of melted chocolate throughout the brownies, adding extra richness and texture.

Pour the batter into a lined baking tin, spreading it out evenly. A square or rectangular tin works best for achieving that classic brownie shape.

Preheat your oven to 180C (350F) and bake the brownies for 25-30 minutes, or until a skewer inserted into the center comes out with a few moist crumbs. Be careful not to overbake, as you want the brownies to be fudgy and moist.

Once they are ready, remove the brownies from the oven and allow them to cool completely in the baking tin.

When the brownies have cooled, carefully lift them out of the tin and cut them into squares or triangles. This step ensures neat and tidy portions that are ready to be enjoyed.