Add cubed cold butter and dry ingredients into your stand mixer bowl.
Cut butter into the flour with the mixer on low until a few dime- and pea-sized pieces remain.
Stream in cold water and mix on low just until combined.
Finish dough by hand on the counter, bringing it together into a single rough mass.
Form dough into a 1”-thick brick, then wrap and chill until firmy set.
Roll dough out to ⅛" to ¼" thick.
Cut into desired shapes and place on lined baking sheets.
Mix cinnamon and sugar together.
Slightly dampen the tops of the cookies with water, and sprinkle generously with cinnamon and sugar.
Bake cookies until deep golden-brown and super-flaky.