Mix sugar thru shortening together. Sift together salt, baking powder, soda, ginger cinnamon and 3-1/2 cups flour. Add to dry to wet alternately with buttermilk or sour milk. You may need to add more flour (I ended up using about 5 cups flour all together). Chill for at least 2 hours.
Remove dough onto floured surface (I do this 1 batch at a time for a total of 3-1/2 batches and using my large airbake I get about 18 cutouts per batch). Place dough you are not rolling back in fridge to keep chilled. Lightly coat dough with flour and shape into a round ball. Roll to about 1/2" thick. Cut with round cookie cutter.
Bake at 350 for 10-12 minutes or until cookie looks dry on top and/or a slight dent remains when touching top of cookie with finger. Cool completely.
To make the frosting: melt butter and mix in with confectioners sugar along with vanilla and 2 tablespoons milk. Add more milk as needed to make spreading consistency.