Peel and finely grate the kohlrabi, carrots and apple – a mandolin with a grater blade is perfect for this, if you have one. Transfer to a wide, shallow serving bowl. Add the lemon juice and the roasted peanuts.
Heat the oil in a small saucepan and add the mustard and cumin seeds. when the seeds start to ‘pop’, remove from the heat and pour over the kohlrabi mixture. season well and toss to mix thoroughly. serve at room temperature.