In a mixing bowl combine all ingredients except cheese, jalapeno and butter. Mix well to completely incorporate making sure to break up crab until smooth. Salt and pepper to taste.
Remove stems from mushrooms and fill mushroom caps with crab mixture
Place 1 slice jalapeno on top of crab mixture and top jalapeno with a very small pat of butter. Place in a preheated 350 degree oven for 10 – 12 minutes.
Right before you take them out of the oven, sprinkle a small amount of the mixed shredded cheese on top of each one and allow it to melt.