Preparation time: Under an hour
Cooking time: A few minutes
Refrigeration time: At least 2 hours

1. In a round stainless steel cake pan lined with plastic wrap, pour in the aspic with the chopped chervil; refrigerate to set;
2. shell the crabs, reserving 300 g (10 oz.) crabmeat; place the gelatine leaves in cold water; make a sabayon with the liquid from the mussels, 3 egg yolks, salt and pepper; 
3. once the sabayon is cooked and very foamy, add the drained gelatin leaves, whisked to dissolve them; incorporate the butter in small pieces; 
4. cool; add the crabmeat and combine;
5. whip the cream; gently fold into the sabayon with a spatula; 
6. pour into the pan; top with the slices of rye bread; put a little of the sabayon on top of the bread and smooth out; 
7. chill for several hours; turn out of the pan and decorate.