Preheat oven at 375-degrees.
In a large bowl, mix the butter, sugar, vanilla, and egg. Stir in the flour, baking powder, and salt.
Divide dough in half. Stir cinnamon into one half until it's mixed in and brown.
Grab equal pinches of both kinds of dough, place them side by side, and gently twist into a short rope. Place on cookie sheet, with several inches around each to account for expansion. Repeat with remaining dough.
Bake 8 to 10 minutes, until the cookie is set with the pale dough just tinted brown. Let cookies cool on wire rack. Store in a sealed container for several days.
OM NOM NOM!