Cream the shortening and sugar. Add the egg and mix well. Mix and sift together the flour, ginger, cinnamon, and salt, and add to the creamed mixture alternately with the milk in which the soda has been dissolved.
Add the molasses. Add the blueberries and pour the batter into a greased and floured pan (9 x 9 square or round cake pan).
Sprinkle the three tablespoons of sugar over the batter in the pan and bake at 350 F or 176 C for 50 minutes to one hour.
The sugar sprinkled over the top makes a sweet crusty topping when the cake is baked. This cake is delicious warm from the oven, cold, and even better when two days old.