Preheat oven to 400F
Remove stems and clean mushroom caps. Cook in boiling water for 6-8 minutes until softened.
Drain and blot on paper towels
Stack phyllo sheets on each other brushing each layer with melted butter before adding additional sheets. Cut lengthwise into 3 and crosswise into fourth's yielding 12 squares
Place 1 mushroom into each square and fill with cheese and nut mixture. Fold opposite corners together and pinch to seal.
Put on ungreased baking sheet, brush with remaining melted butter and baked for 11-13 minutes or until golden brown. Serve warm.