In a small saucepan, combine the water, butter, sugar and salt and bring to a light boil. Once the mix is boiling, remove the pan from the heat and dump all the flour in at once. Beat with a spoon quickly until all the flour is mixed in.
Place your dough ball into the base of a stand mixer fitted with a paddle attachment and being beating the mix to help cool it down slightly.
Place your beaten eggs into a pouring vessel (like a liquid measuring cup) and start slowing mixing the eggs into the dough a little at a time. Allow the eggs to fully combine before adding more, and check about half way through to see how moist the batter is. You will likely only need a bit more than half depending on your egg size. The batter should be stiff enough to be piped while holding its shape.
TIP: I test the consistency by taking a bit of dough between my thumb and forefinger, and if you see a nice v-shape when you separate your fingers you're probably in a good place.
To pipe your churros you have two options. You can either pre-pipe the churros into a shape or free pipe directly into the oil. I prefer to pipe onto a small piece of parchment and then fridge to retain the nice ridges and also do a bit of prep work so I can enjoy a fresh hot churro for dessert.
Fill a piping bag, fitted with a large star tip, with your churro mix. If pre-piping, set out roughly 5"x5" squares of parchment onto a baking sheet. Pipe your churros into a tear drop shape and set in the fridge to chill until ready to fry.
Mix your cinnamon and sugar in a shallow bowl and set aside to coat your churros.
Heat your oil to 370° and set aside some paper towel to drain the churros.
Drop the churros into the fryer, parchment and all, fry for 1.5-2 minutes per side, flipping once. The parchment will quickly separate from the churro and can be removed with tongs.
Once fried place your churros on the paper towel to drain for 30 seconds, then quickly pop them into the cinnamon sugar to coat while hot.