1) Add butter to a saute pan and add chopped mushrooms over medium heat. Cook for 5-7 minutes until cooked. Then chill mushrooms until very cold.
2) Once cold, add all ingredients to a food processor except cream. Pulse a few times. Add in cream last and pulse until it’s a somewhat smooth paste.
3) Lay down some plastic wrap on top of a cheesecloth layer. Add a layer of the mushroom mixture to the plastic wrap and then place a center column of salmon down the center of the mousseline.
4) Roll up the mousseline tightly. This won’t be easy, but try to get it evenly distributed.
5) Tie ends with butchers twine and lightly poach the mousseline in 180-200 degree water for 30 minutes.
6) Chill the mousseline after cooking with some light weight on it to keep it compressed.
7) Let the mousseline chill over night and serve the next day with crackers.