Heat butter, water, and salt in a pot. Once butter melted, slowly work in flour until mixture becomes a paste.
Leave mixture to chill for at least 5 minutes.
Add in egg and vanilla to the mixture and mix.
Pipe mixture out into any shape onto parchment paper. Alternatively pipe directly into hot oil.
Fry at 375ºF for a few minutes till golden brown.
Leave to rest for 5 minutes.
Sprinkle sugar and cinnamon mixture over churros.