Cook the asparagus in about 1 litre of boiling salted water until tender (around 5 mins). Reserve the liquid. Cut off the tips and reserve for decoration. Puree the asparagus stems.
Toss the lamb in the seasoned flour. Fry the onions and meat in the butter until browned.
Gradually blend in about 1 litre of the reserved cooking liquid. Leave to simmer until tender (1 hour or so). Skim any surface fat.
Stir in the asparagus puree and cream. Season to taste with salt and pepper and lemon juice. The sauce should be fairly thick. Serve garnished with the asparagus tips.
