Boil the kettle, then measure 300ml boiling water into a jug and add the melted lactose free butter and vanilla extract.
Sift the gluten free flour and baking powder into a large mixing bowl with a generous pinch of salt.
Make a well in the centre, then pour in the contents of the jug and very quickly beat into the flour with a wooden spoon until lump-free.
Cut out 6 10cm x 10cm squares of baking parchment and grease them well with oil. Transfer the churro batter to a piping bag fitted with a large star nozzle, and pipe spiraled circles of batter onto the parchment.
This is easiest if you start from the centre, and swirl the nozzle round and round until you reach the edge of the paper, avoiding any gaps. Chill for 45 mins, or up to 2 hrs, until the batter feels firm to the touch.
Fill a large deep saucepan one-third full of oil. Heat until a cube of bread browns in 45 seconds – 1 min (about 180C). Cover a tray with kitchen paper and mix the caster sugar and cinnamon together.
Remove the churros from the fridge and drop 2 or 3 directly into the pan, discarding the parchment. Fry until golden brown and crisp, then remove with a slotted spoon and drain on the kitchen paper-lined tray.
Carry on cooking the rest of the dough in batches, sprinkling the cooked churros with some cinnamon sugar as you go. Once you’ve cooked all the churros, toss with any remaining cinnamon sugar and sandwich with balls of your lactose free ice cream