Julienne peelers look like ordinary peelers, but the blade has serrations to cut slices into matchsticks. They’re available from kitchen shops and Asian grocers. You can cut carrot into matchsticks with a knife. Cut carrot into 5cm lengths, cut lengths into thin slices; stack two to three slices together, cut into thin matchstick like strips. Pickle red onion and carrot a day ahead; refrigerate until ready to use.