Peel the asparagus and cook in boiling water until tender.
2
Meanwhile, melt the butter and place the egg yolk in a stainless steel bowl and whisk together with 150ml (1/4pint) boiling water until a sabayon is formed. Pour onto the melted butter slowly as for mayonnaise. Season with salt, pepper and lemon juice.Garnish with a chervil and tomato concasse.