Preheat oven to 350. Thaw fish fillets if frozen. Rinse and drain well. Cut into four 4x3 inch portions. Place in a shallow baking dish.
Cook onion and mushrooms in margarine or butter, covered, about 5 minutes. Uncover; add peas and simmer for 2 to 4 minutes or till excess liquid evaporates. Remove from heat.
Stir in cream cheese, dillweed, and pepper. Spoon mixture evenly over each fish portion.
Separate refridgerated crescent rolls into 2 rectangles. Pinch perforations to seal. Cut each rectangle in half. Place one rectangle atop each fish portion.
Brush dough with milk or butter if desired. Bake in preheated oven for
20-25 minutes or till fish is done.
*This dish can be transformed into an even more delicious and more formal dish by adding crab meat or even shrimp along with the vegatables/cream cheese to make a seafood stack. You can also make a crab or lobster Newberg sauce for the top just before serving.