Preheat your oven to 180°C (350°F) or 160°C if using a fan-forced setting.

Lightly grease a 20cm (8-inch) square baking tin with oil, then line it with parchment or baking paper, leaving an overhang on the sides for easy removal (see Note 2).

Combine the butter and dark chocolate chips in a heatproof bowl. Microwave in 30-second intervals, stirring between each burst, until fully melted and smooth—this usually takes around 1 minute 30 seconds.

Stir in the brown sugar and vanilla extract. Add the eggs and mix thoroughly until the batter is glossy and smooth.

Add the flour, cocoa powder, and a pinch of salt, stirring just until everything is combined. Fold in the chopped dark chocolate chunks, then pour the batter into your prepared tin.

Bake for 24 minutes if you want a very gooey center, 28 minutes for a fudgy but still ultra-moist texture (my personal favorite, as shown in the video and photos), or 32 minutes for a moist, more cake-like fudgy brownie. (See the blog post for examples using the toothpick test.)

If you choose to skip the extra chopped chocolate chunks, reduce the baking time by 2 minutes.

Allow the brownies to rest in the tin for 10 minutes before lifting them out. Let them cool for at least 20 minutes before slicing.

Store in an airtight container at room temperature for up to 4 days (though they’re likely to disappear much faster!) or freeze them for up to 3 months.