Boil the beets until tender (knife easily inserts into the centre), remove from water and allow to cool, gently remove the skin and slice into 7mm thick discs.
Remove rind from the oranges and slice into 7mm discs.
Arrange beet and orange slices, overlapping on a serving dish.
Whisk together the dressing ingredients and drizzle over, then sprinkle on the crumbled feta and mint leaves.