In a large bowl, mix molasses and butter; add eggs and beat until well-blended.
Add beer alternately with flour.
Stir in raisins, walnuts, baking soda and seasonings.
Pour into a 9x13x2 inch baking dish.
Bake at 350Â°F for 45 to 50 minutes.
Remove from oven, cool and dust with icing sugar before serving.