1. To make the streusel: place sugar in a medium bowl. Sift together flour, salt, cinnamon, nutmeg, and ginger on a sheet of wax paper and add to sugar. Work in butter with fingers until the texture resembles coarse sand.

2. Make the crust. Coat a 9 inch ovenproof glass pie pan with vegetable spray. Roll out pastry dough. Fit into bottom of pie plate and trim off excess. Chill in refrigerator.

3. Set the oven rack in the middle position. Preheat the oven to 400 degrees F.

4. Place molasses in a bowl. Dissolve baking soda in water and add to molasses, stirring with a wooden spoon. Pour into prepared pie shell.

5. Sprinkle streusel over surface of pie and bake 15 minutes. Reduce oven temperature to 350°F and bake another 25 minutes, or until a tester inserted into pie comes out clean.

6. Place pie on rack and cool completely before cutting. Store leftover pie loosely wrapped in wax paper in the refrigerator.