Bring a saucepan of water to the noil then using a sharp knife mark a cross on the base of each tomato. Blanch in boiling water for 10 seconds. Remove from the water and refresh under cold running water.
Peel the tomatoes then slice off their tops and scoop out the seeds and pulp.
Mix the shrimps with the chives and pack about half of them into the tomatoes. Put the tomatoes on two serving plates and top with the mayonaisse.
Toss the lambs lettuce in vinaigrette and arrange around the tomatoes, with the remaining shrimps.