Preheat the oven to 180C/355F/Gas 4.
Place the pears into a roasting tray and drizzle with the olive oil. Toss well to coat, then season with salt and freshly ground black pepper. Roast in the oven for 8-10 minutes, or until golden-brown and softened. Set aside to cool.
Place two pear halves into a food processor along with the honey, cider vinegar and extra virgin olive oil. Blend until smooth, adding a little warm water if the purée is too thick.
To serve, slice the remaining pears and divide among four serving plates. Curl the ham into cones and place on top of the pears, then spoon over the pear dressing and top with the chopped pickled ginger, lemon thyme, cheese and chopped walnuts.