Preheat the oven to 180oC/350oF/Gas
4. Line the base and sides of a 20cm square baking tin with greaseproof
paper and grease the paper.
Gently melt the butter or margarine in
a small saucepan. Remove from the heat and stir in the cocoa powder.
With an electric mixer, beat the eggs, sugar and vanilla together
until light.
Add the cocoa mixture and stir to
blend.
Sift the flour over the cocoa mixture
and gently fold in. Add the walnuts and raisins and scrape the mixture
into the prepared baking tin.
Bake in the centre of the oven for 30
minutes. Leave in the tin to cool before cutting into 5cm squares and
removing.