Cut the cheese into 8 pie pieces the day before or possibly as early as possible. Place the pieces separately in a dish. Drizzle with the Marc d’Alsace and season heartily with fresh pepper.
Clean the spring onions and cut them into fine rings. Pluck off about 2/3 of the chervil leaves and chop.
Mix crème fraîche and whipped cream. Stir in mustard, spring onion slices and chervil. Pour over cheese and refrigerate, covered with plastic wrap, for one night.
Chop remaining green onion and chervil leaves as directed. Form over cheese and bring to table.