Peel and finely grate the kohlrabi using a box grater and place into a large mixing bowl. Using a sharp knife top and tail the celeriac, peel the skin off and cut in half. Using a vegetable peeler shave half of the celeriac into the mixing bowl. Reserve the other half for later use.
Finely shred 1/4 of red cabbage and place into the mixing bowl. Thinly slice the red chilli and add to the mix. Dress the slaw with the juice of the blood orange and lemon, salt and pepper and mix thoroughly using your hands until everything is evenly coated.
Place the slaw onto a large serving platter and give a final drizzle of extra virgin olive oil and scatter the tarragon leaves over the top.