Stir together flour, baking powder, sugar, cream of tartar, and salt.
Cut in 1/4 cup of butter and the shortening until mixture resembles coarse crumbs.
Add milk and stir just until dough clings together.
Knead gently on floured surface and form into balls (about 1″ diameter).
Bake at 450 degrees for 10-12 minutes.
Roll baked biscuit balls in cinnamon/sugar mixture.
Melt 1/4 cup butter.
Roll baked biscuit balls in melted butter and then in cinnamon/sugar mixture.