Heat 2 cups of milk until steaming in a saucepan
Whisk together egg yolks, sugar, and cornstarch in a bowl
Whisk and heat egg mixture into milk until pudding like
Remove from heat and stir in vanilla and butter
Seal with plastic wrap touching the surface to prevent a skin from forming, and refrigerate until completely cool
In a large bowl, combine warm milk, heavy cream, sugar, yeast, and egg
Knead in flour and salt until smooth and elastic; add softened butter gradually
Cover and let rise until double in size (1.5 - 2hrs)
Combine cinnamon sugar spread ingredients and mix until a smooth paste
Roll out the dough into a roughly 24 x 16 inch rectangle
Spread custard and cinnamon paste on dough
Fold into thirds and cut into 10 - 12 strips, ~ 1 - 1 ¼ inches in width
Twist into a helix, and wrap into a bun shape
Let rise for ~1 hour on a baking sheet until puffy
Egg wash the buns
Bake at 200 C (~390 F) for 20 - 25 mins, or until golden brown
Let cool for 2 - 3 mins and brush each bun with the sugar syrup
Let cool completely before packaging
