Heat cream and milk, whisk yolks with sugar, temper, cook custard, add vanilla & cinnamon, chill.
Boil water, butter, salt, stir in flour, cool, beat eggs, pipe, fry churros, roll in cinnamon sugar.
Churn chilled custard, add churro pieces in last 5 min.
Transfer to container, layer churros, cover with plastic wrap, freeze.