Mash the goat cheese and add it to the milk mixture, along with the Parmesan and herbs. Stir until smooth and remove from the heat. Cool for a few minutes and then stir in the egg yolks. Season to taste with salt and pepper.
Separately beat the egg whites to stiff peaks and fold quickly into the cheese mixture. Divide the mixture among the buttered dishes and smooth the surfaces. Place the dishes in a baking pan with raised sides, and pour boiling water into the pan to come two-thirds up the sides of the soufflé dishes. Transfer to the preheated oven and
With your fingers, gently ease the soufflés out of the dishes and place them in a lightly buttered, ovenproof dish just large enough to hold them so that they are not touching. Cover loosely with plastic until ready to serve.
Arrange the watercress on plates. Place a warm soufflé in the middle of each plate. Pour the warm cream over the soufflés and sprinkle the tomatoes and lemon zest over them. Serve immediately.