Preheat the oven to moderate 180c ((350f/ Gas 4).

Lghtly grease a 20x30cm baking tin and line with baking paper, hanging over the two long sides.

Place the dates in a saucepan with 200 ml of water.

Bring to a boil, then reduce the heat and simmer gently for 10 mins.

:- Make sure the water doesn`t evaporate completely.

Add the bicarbonate of soda and leave to cool.

Place 185 g of the butter, the flour, vanilla, baking powder, eggs and 75 ml of the milk in a food processor and mix in short bursts for 1 min, or until well blended.

Add the dates and pulse to blend.

:- DO not overprocess!

Place the mixture in the tin and bake for 20 mins, or until a skewer inserted in the centre comes out clean.

Set aside to cool.

Place the remaining butter and milk and the brown sugar in a pan and heat gently to dissolve the sugar.

Add the icing sugar and mix well.

Spread over the cooled slice and sprinkle with the walnuts.