Lightly grease a 5x9-inch loaf pan using a little of the margarine.

Place the remaining margarine, sugar, cocoa, vanilla, and soy milk in a heatproof mixing bowl, or the upper part of a double boiler.

Place the bowl or boiler over simmering water and stir until smooth.

Add the nuts if desired.

Pour the mixture quickly into the prepared pan.

Chill thoroughly and cut into squares.

Chill at least one hour, but for best results chill overnight as the fudge will be firmer and more like regular fudge.