Cut the PVC piping into six 7 cm (2¾ inch) long pieces. Cut the acetate into six 10 × 7 cm (4 × 2¾ inch) rectangles. Roll each piece lengthways, then place inside a piece of PVC pipe. Make sure one end of the acetate sits flush with the pipe and the other end protrudes. Place plastic wrap over the flush end and secure with tape. Stand, covered-end down, on a tray.
Place the juice, eggs, cream and sugar in a Thermomix and cook at 80°C (176°F) for 8 minutes. Alternatively, place in a double boiler over simmering water and whisk continuously for 15 minutes or until thickened and the mixture reaches 80°C — make sure it doesn’t overheat or it will split. Soak the gelatine in cold water for 5 minutes or until softened, then squeeze out the excess water and add the gelatine to the rhubarb mixture, stirring until dissolved.
Pass through a fine sieve and spoon into the moulds. Refrigerate for 8 hours or until set.