1. Soak the gelatin in a little of the beetroot liquid, and when soft, stir it into the rest of the liquid and the sherry vinegar. Heat gently, stirring until the gelatin has dissolved. Cool as quickly as possible, outside the back door, on a balcony or over a bowl of ice. Wet a ring mould, and scatter the beetroot in it. Pour over the cold liquid, and refrigerate until set. The jelly can be prepared the day before required.
2. Scrub and boil the potatoes, and while they are cooking, make the dill cream. Strip the feathery leaves from the stems, which can be put in with the potatoes for flavour. Put the leaves in a mortar with a pinch of sea salt and some pepper. Grind with a pestle until you have a paste. Fold this into the creme fraiche or whipped cream.
3. To assemble the salad, turn the jelly out onto a platter. Fill the centre with potato salad mixed with some of the dill cream. Arrange the eel fillets on top, and garnish with more dill. Alternatively, slice the eel and some shallots, and fold the mixture, together with the cream into the potatoes.
4. There are other ways of serving this combination. The simplest is to dress the chopped beetroot with sherry vinegar and walnut oil, and put it in the bowl. Serve the remaining ingredients, smoked eel, potatoes and dill cream in separate bowls too, and forget about the jelly.
5. If you do not have a ring mould, the jelly can also be set in individual glass bowls or china dishes, and the salad, eels and cream piled up on top.