Wash and clean the tomatoes and spring onions. Halve the tomatoes and cut the spring onions into rings. Halve avocado, remove stone. Remove the flesh from the skin and cut crosswise into slices, sprinkle with lemon juice. Drain shrimps on a sieve. For the sauce, peel and finely dice the shallot.
Mix salad cream, yoghurt, ketchup, brandy and shallot. Season the sauce with salt, pepper and sugar. Carefully mix vegetables and shrimps, distribute in 4 glasses. Pour sauce over them. Garnish with chervil