Wash and peel the asparagus and cut off the woody ends. Asparagus spears may be cut in half. Boil up plenty of water, a little salt, sugar and 5-10 g butter in a large pot. Add the asparagus to the boiling water, cover and cook for 15-20 minutes.
Cut the graved salmon into about 12 large cubes. Peel and finely dice the onion. Remove cooked asparagus from the stock, drain and keep warm. Mix flour and 10 g soft butter. Melt 20 g butter and crustacean paste in a pot while stirring.
Fry the onion in it. Measure 400 ml asparagus stock and pour it into the crustacean paste while stirring. Bring the sauce to the boil. Add cream and flour butter and simmer for 3-4 minutes at medium heat while stirring.
Arrange asparagus with crab butter cream and gravlax on plates. Garnish with dill, lemon wedges and zest. Serve with new potatoes.