Place a chefs' ring onto a plate and drape one slice of the prosciutto over it. Press down in the middle, pushing the meat against the inside of the ring, leaving some of the prosciutto to hang over the edges. Repeat with a second slice of prosciutto, this time placing the slice so that it covers the other sides of the ring (from above, the two slices should intersect to form a 'cross').
Chop the remaining slice of prosciutto and mix together with the cream cheese, chive flowers, pear and tomato and press into the chefs' ring. Bring the overhanging ends of prosciutto over the top to form a parcel, then carefully invert the mould onto a serving plate.
For the dressing, place all of the dressing ingredients into a food processor and pulse until smooth. Pass through a sieve, then spoon the dressing around the edges of the plate. Garnish with chives and serve.