Peel and finely slice the beetroot, place it in a shallow dish, season with salt and plenty of pepper, scatter over the shallot, balsamic vinegar and oil. Cling film and store in the fridge for 24 hours. For the dressing combine the mustard, vinegar, cream, dill and a seasoning of salt and pepper and set aside.

To serve arrange the beetroot on plates and top with the rollmop and then drizzle over the dressing.