Step 1

Pre-heat oven (180 °C, Fan 160 °C, 350 °F, Gas 4), grease and line a 20x20cm (8x8 inch) square baking tin with baking paper.

Step 2

In a large bowl sift together the dry ingredients (flour, sugar, cocoa powder, baking powder, salt), then stir in liquids (soy milk, melted margarine, treacle) until a smooth batter forms. Finally, mix in walnut pieces.

Step 3

Pour batter in to the lined cake tin, smoothing it out and distributing the walnuts evenly.

Step 4

Bake in the centre of the oven for 30-35 minutes. Towards the end of this time test by inserting a cocktail stick into the middle of the cake. It should come out clean. If there is wet batter on the stick, return it to the oven and cook for a couple of minutes more, then test again. Repeat as needed until the stick comes out clean.After 10 minutes remove the cake from its tin and leave to cool completely on a wire rack before slicing.