Pre-heat oven to 170°C.Grease and line a 30 x 15cm slab tin.
In a large bowl combine the flour, brown sugar, cocoa powder, choc bits and walnuts. Mix thoroughly and make a well in the centre. Whisk together the vanilla, eggs and water, and then pour the mixture onto the dry ingredients.
Pour the melted Copha into a bowl and mix all ingredients together until just combined. Do not over mix.
Spoon mixture into the greased and lined baking pan and smooth the surface. Bake the brownies in the preheated oven at 170°C for 30 minutes. The centre should still be moist.
Remove from oven and cool on a wire rack. Once brownies have cooled, cut into squares using a sharp knife and dust with icing sugar or drinking chocolate.