Thinly slice the cauliflower florets using a mandolin or with the slicing attachment of a food processor. Discard all the really tiny bits of the cauliflower and keep the slices.
Make the orange tahini salad dressing by whisking together all the ingredients in a bowl and setting aside.
Assemble the salad staring with the mixed leaves, then add the cauliflower, the oranges, seeds and nuts and drizzle on the salad dressing.