Preheat the oven to 350 degrees F.
Sift the flour, baking soda, and salt into a bowl.
With a handheld or standing mixer, beat together the shortening and butter. Add the 1 1/2 cups sugar and continue beating until light and fluffy, about 5 minutes. Add the eggs, 1 at a time, beating well after each addition. Add the flour mixture and blend until smooth.
Mix the 3 tablespoons sugar with the cinnamon in a small bowl. Roll the dough, by hand, into 1 1/2-inch balls. Roll the balls in the cinnamon sugar. Flatten the balls into 1/2-inch thick disks, spacing them evenly on unlined cookie sheets. Bake until light brown, but still moist in the center, about 12 minutes. Cool on a rack.
Yield: about 20 cookies