Method 1. Gently cook the leeks in the stock with the caraway seeds, garlic, thyme and bay leaf until tender. Season to taste with salt and pepper.
Preheat the oven to 200C/gas 6 3. Peel the potatoes and celeriac and slice them very thinly into rounds, using a sharp knife (or use a mandoline slicer or slicing attachment on a food processor) keeping the two vegetables separate.
Season the potato and celeriac rounds with salt and pepper and sprinkle with olive oil.
Bake separately on oiled non-stick baking trays for about 10 minutes, until just beginning to colour and soften. Drain and allow to cool.
Place 3 large sheets of foil on top of each other. Smear the top layer with the butter and season lightly with salt and pepper.
Place a layer of overlapping potato rounds in a rectangle about 40x30cm on the buttered foil and season to taste with salt and pepper.
Cover one half of the potato rectangle with the celeriac rounds.
Lay the leeks on top and season with salt and pepper.
. Cover the leeks with a layer of overlapping basil leaves.
. Place the goats' cheese between two sheets of cling film and roll with a rolling pin to flatten. Remove the cling film and season the cheese with freshly ground black pepper.
. Place the goats' cheese on top of the basil leaves. Cover with the remaining celeriac rounds. Finish with a layer of mozzarella slices.
. Roll up in the foil like a swiss roll. Wrap the roll as tightly as you can in several layers of cling film, twisting the ends like a Christmas cracker. Alternatively, you can use just foil.
. With a sharp knife, puncture the cling film all over, through to the foil.
. Holding the twists of cling film at each end, squeeze the excess juices out through the holes. Continue squeezing until no more juices run out. Ideally hang the roll in a cool place for 24 hours. This is important, as the terrine will later be sliced and fried and if there is too much liquid, the outer layer of potato won't crisp up.
. Place the roll in the fridge until ready to cook 17. Slice the roll into 4cm thick slices through the cling film and then return the slices to the fridge for 10 minutes.
. Remove the cling film and dust the slices with flour.
. Heat the oil in a frying pan and cook the terrine slices on both sides until crisp and golden.
. To make the piperade dressing; heat the oil in a pan and cook the aubergine, cherry tomatoes, spring onions, chill strips and capers until soft.
. Drizzle the sun-dried tomato oil and basil oil on a serving plate.
. Serve the dressing with the terrine slice. Garnish with the cubed lemon segments and chervil.