Preheat oven to 350 F.
To make the cookies, cream together sugar, butter, and shortening.
Mix in egg, buttermilk and vanilla extract.
In a separate bowl, sift together flour, baking powder, baking soda, and salt.
Add dry ingredients into wet ingredients and stir until a soft dough forms.
Place dough in a plastic bag and flatten.
Refrigerate for 1-hour or longer. (This step is a MUST. Overnight is best.)
Meanwhile, make the cinnamon mixture by combining brown sugar and cinnamon. Set aside.
When the dough is chilled be ready to work quickly. (The dough gets sticky as it warms up. It must remain super cold while handling)
Mix together 1 tablespoon of flour + 1 tablespoon of powder sugar and generously flour a nonstick work surface (like a silicone baking mat or parchment paper) with some of the mixture. Be sure to also coat your hands and rolling pin.
Roll cold dough out into a 12X 9 rectangle about 1/4-inch thick. (Be sure to keep your hands and the rolling pin coated well in the flour-sugar mixture.)
Brush the surface of dough with melted butter.
Immediately sprinkle on brown sugar mixture in an even layer. Press it down into the dough just a bit.
Starting with the longest side, gently, but quickly roll dough into a tight log. (keep your hands floured and add more flour mixture to the nonstick surface if needed)
Roll log in plastic wrap and place on a pan/tray.
Freeze for 30 minutes or until the roll is firm enough to cut without squishing when you cut it.
Carefully slice the cookies about 1-inch thick using a serrated knife. ( I cut off the ends first since they are never pretty)
Place cookies on parchment paper 2-inches apart.
VERY IMPORTANT: Press the cookie rolls gently so that they are tighter. Seal the ends of the cookies by pressing them into the dough. (This will keep the cookies from unraveling while baking. Make sure the cookie roll is wrapped nice and tight.)
Bake for 10-12 minutes (cookies MUST be cold when going into the oven.) Refrigerate the leftover dough until ready for the next batch so that they stay cold. (Check on the cookies at the 6-minute mark to make sure they are not unraveling. If they are, pull them out and quickly press the seam back together with a back of a spoon)
Meanwhile, prepare the glaze by combining cream cheese, butter, powdered sugar, milk, and vanilla.
When cookies are ready (they will be slightly underdone), let them sit on the baking sheet for 2 minutes before transferring to a cooling rack.
Carefully brush hot cookies with glaze, allowing the glaze to melt down into the folds of the cookie.
Let glaze set and then store cookies in an airtight container between rows of parchment paper.