Preheat oven to 200°C fan bake. In a pot, combine the water, vanilla and butter and place over a medium heat. Stir until the butter has melted and bring to a simmer.
Using a wooden spoon, stir in the flour and salt and mix until smooth. Stir over the heat until a dough ball forms, then remove from the heat and leave to cool slightly.
Continuing with the wooden spoon, beat in eggs one at a time; ensuring each egg is fully incorporated before adding the next. Once the mixture reaches a thick consistency that just drops from a spoon, transfer to a piping bag fit with a wide nozzle.
On a paper lined baking tray, pipe the mixture into 10cm long logs, at least 5cm apart. Use one finger, wet with water, to press the end into a smooth shape and place into the oven and bake for 25-30 minutes or until golden brown in colour.
Leave to cool slightly, then transfer to a rack and leave to cool completely.
To fill the eclairs, cut in half horizontally and melt the 100g white chocolate. Fill the eclairs with Tatua Caramel Mousse, then drizzle with white chocolate or dust with icing sugar and garnish with sprinkles. Serve immediately, or fill at a later time to preserve the unfilled eclairs.