Preheat oven to 220C. Spoon choux pastry into a piping bag fitted with a 20mm plain nozzle. Pipe 12cm-long strips onto a baking paper-lined oven tray. Bake for 15 minutes, then reduce heat to 180C, prick pastries with a skewer or tip of a small knife and bake until golden (about 5 minutes). Cool on a wire rack to room temperature, then halve lengthways and set aside.
Meanwhile, combine chocolate and 50ml cream in a small saucepan and stir over low heat until chocolate melts and mixture combines. Stir in vegetable oil and set aside.
Whisk remaining cream, icing sugar and vanilla paste in a bowl until soft peaks form, then spoon into a piping bag fitted with a 20mm nozzle and pipe into prepared pastries. Spread éclair tops with chocolate mixture and serve immediately.