Place the chicken legs in a large roasting tin, drizzle with oil and season with salt and pepper. Roast for 35–40 minutes, until cooked through. Set aside to cool.
Meanwhile, heat the duck fat in a large saucepan to 70C and confit the artichokes, fennel and garlic bulbs for 2 hours, until soft.
Discard the chicken skin, remove the meat from the bones and place in a bowl. Chop the confit fennel very finely and add to the chicken with the lemon zest, thyme, basil, and tarragon. Squeeze the garlic from its skins into the bowl, season with salt and pepper and mix well.
Line a large terrine mould with cling film, and lay the Parma ham slices width-ways along the mould so that each slice hangs over the edges.
Place half of the chicken mixture into the mould. Slice the artichokes and press them in a neat layer over the chicken. Top with the rest of the chicken, fold over the Parma ham and the cling film. Press with a weight such as tins of tomatoes and leave to set in the fridge overnight.
When ready to serve, turn out onto a board and remove the cling film. Use a sharp knife to cut slices and serve with some salad leaves on the side.