Preperation:

Preheat oven to 350 °F (180 °C).

In large frypan, melt butter. Sauté onions, mushrooms, carrots and celery until vegetables are tender-crisp and liquid has evaporated; add salt to taste.

Cut aluminum foil into four 12 inch (30 cm) squares; place shiny side up. Distribute vegetable mixture over centre of each square; top with fish. Sprinkle 1 tsp (5 mL) lemon juice over each serving. Fold half of foil over to form triangle and seal edges.

Place packages on shallow baking sheet. Bake 15 minutes or until fish flakes with fork. To serve in foil, cut 'X' opening with scissors in top of each package.