Begin by heating 6 tablespoons of butter, half a cup of milk, half a cup of water, 1 tablespoon of sugar, and a splash of homemade vanilla extract together.
Add 1 cup of all-purpose flour and stir continuously until the mixture forms a smooth dough.
Cook the dough gently for a short while.
Incorporate 3 eggs one at a time, mixing thoroughly until the dough is smooth.
Transfer the dough into a piping bag.
Fry the churros in oil heated to 350°F (about 175°C) until they are golden and crisp.
Sprinkle the fried churros with cinnamon sugar.
Fill the churros with Nutella using a syringe or piping bag.
Alternatively, serve with Nutella on the side for dipping.