Place the flour, cocoa, both the sugars, the butter, vanilla and eggs in a large bowl and mix until smooth.

Add the chocolate and stir to combine.

Preheat oven to 160°C (325°F).

Lightly grease a 20cm square tin and line with non-stick baking paper.

Spread the mixture into the tin.

Bake for 50 minutes to 1 hour or until the brownie is set.

Allow to cool in the tin for 5 minutes before slicing into squares and serving warm, or allow to cool completely in the tin.