To make your dressing, add the capers, garlic, shallots and chilli pepper in large jar with the red wine vinegar and stir and allow to sit for five minutes. Now add the mustard, citrus juices, parsley and olive oil, place lid on and vigorously shake. Adjust with salt and pepper, shake again and reserve.
Clean the mussels by rinsing under cold water, scrubbing and rubbing the shells and pulling the beards out. Rinse once again and discard any that do not close or cracked.
Place the olive in large pot over high heat and once hot, add the mussels, wine and cover. Steam for about 5-6 minutes or until mussels have opened (discard any that have remained shut). Strain from the liquid (save/store to use as stock for another time) and allow to cool.
Open each mussel, discarding one shell from each and separating the meal from the other shell. Place the mussel meat back on each half-shell and arrange on plates or a platter.
Shake the dressing once again and before serving, spoon over the dressing and serve with an Agyros Atlantis White.