1. Preheat the oven to 180 degrees. Melt
half of the butter with the dark
chocolate in a thick-bottomed pan,
and melt the white chocolate in
another pan with the rest of the
butter. Leave to cool.
2. Using the mixer, beat the eggs briefly
with the sugar and vanilla. Divide the
flour into 2 portions and add a pinch
of salt to each.
3. Beat half of the egg-sugar mixture through
the dark chocolate. Then add in half of the
flour and half of the nuts and mix. Do the
same with the white chocolate mixture.
4. Pour the white and brown brownie mixture
into two different sides of the cake tin. Use a spatula to partially mix the two colours,
creating a swirl. Bake the brownies for
about 30 minutes.
When ready, the surface should be dry to touch.