Clean and wash the fennel, cut into thin slices, cook in boiling salted water for about 3 minutes and drain well on a sieve. Wash and halve the tomatoes. Cut the cress from the bed, wash and dab dry with kitchen paper. Grate cheese finely.
Beat the egg white with the whisk of the hand mixer until stiff. Fold the grated cheese and half of the cress into the egg white and season with salt and pepper. Fill the fennel, tomatoes and capers into four ovenproof moulds, spread the egg-cheese foam on top and bake in the preheated oven (electric cooker: 200°C/ gas: level 3) for approx. 10 minutes. Serve sprinkled with the remaining cress and garnish with a nasturtium blossom as desired