1 pound large mushrooms
3 tablespoons butter
2 tablespoons finely chopped onion
1 (3 ounce) package cream cheese, softened
2 tablespoons prepared Dijon?style mustard
6 1/2 ounces crab meat
1/4 cup chopped water chestnuts
2 tablespoons chopped pimento peppers
4 tablespoons grated Parmesan cheese

Preheat oven to 400 degrees F. Remove stems from the mushrooms, retaining the caps.
Chop the stems. In a medium saucepan, melt the butter. Brush the mushroom caps with melted butter. In the remaining butter, cook and stir the chopped mushroom stems and onions until tender. Gradually mix the cream cheese and mustard into the saucepan. Continue stirring until smooth. Stir in the crab meat, water chestnuts and pimentos. Heat until warm. Stuff the mushroom caps with the crab meat mixture. Sprinkle the stuffed caps with Parmesan cheese. In a shallow pan, bake the caps at 400 degrees F for 10 to 15 minutes or until hot.