Place the crab into a medium bowl. In a separate bowl, combine egg, mayonnaise, mustard, crackers, crab boil seasoning, and Worcestershire sauce. Mix well. Gently fold mixture into the crab.
Place crab mixture equally on top of each portobello mushroom. Top each center of the stuffing with a 1/4 teaspoon of butter. Refrigerate for 2 hours.
Preheat over to 380 degrees F. Bake for 15 minutes, then place under the broiler for 2 minutes. Sprinkle with paprika. Serve with your favorite garnish, perhaps sliced lemon, tomato or cucumber.