Preheat the oven to 180 C / Gas 4. Grease an 18cm/7 inch square cake tin. Line base with baking paper.
Chop the white chocolate into small chunks. Break the dark chocolate into bits and put into a heatproof bowl with the butter and heat over a pan of simmering water until melted and smooth. Stir and leave to cool slightly.
Stir in the sugar, vanilla and the salt, then gradually stir in the eggs. Stir well until blended.
Sift the flour and cocoa into the mixture and beat well until smooth. Stir in the white chocolate chips. Transfer to the tin and smooth the surface.
Bake for 35 to 40 minutes, until the top is evenly coloured, and a skewer comes out semi-clean when inserted into the centre. Remember the brownies should still be fudgy inside!
Leave to cool in the tin. When they have done so cut into 12 squares.
Serve with custard, ie cream, cream or a hot chocolate sauce for a very scrummy pud!!!
If you are not a fan of white chocolate you can use milk choc chips instead!!!