Preheat oven to 180 C / Gas 4. Grease baking trays.
In a medium bowl, cream the margarine and sugar until smooth. Add the egg and vanilla; mix until fluffy. Stir in the pumpkin puree. Sieve together the flour, bicarbonate of soda, salt, pumpkin pie spice and cinnamon; stir into the pumpkin mixture. Finally, stir in the raisins and walnuts.
Drop cookie dough by heaped spoonfuls onto the prepared baking trays. Bake for 10 to 12 minutes in the preheated oven, cookies should be light brown around the edges. Brush with the spice glaze and transfer to racks to cool.
To make the spice glaze, mix icing sugar with 2 tablespoons of warm water until there are no more lumps. Stir in the 1/2 teaspoon of cinnamon. If the glaze is too thick, add a little more water.