Blend milk, egg yolks, sugar, cornstarch, and flour together in a blender until smooth. Pour milk mixture into a large pot over medium heat; add cinnamon stick and stir with a large wooden spoon. Stir raisins, vanilla extract, and butter into milk mixture; whisk mixture until thickened and smooth, 10 to 15 minutes.

Ladle pudding into bowls and top with ground cinnamon.