Remove stems from mushrooms; reserve.
Simmer mushroom caps and stems in boiling water for 2 minutes.
Drain; invert caps on paper toweling.
Chop enough stems to make 1/2 cup (save remainder for another use).
Combine cheese and dry dressing mix; stir in nuts and chopped stems.
Spoon into caps; place in shallow baking pan.
Sprinkle with paprika, if desired.
Bake in 425° oven 6 to 8 minutes.