Stuffing: Place bread cubes in a single layer on a rimmed baking sheet and bake at 450°F (230°C), stirring occasionally, until toasted, about 4 minutes.
Heat oil on low in a medium nonstick skillet. Add garlic and lemon zest, stirring for about 30 seconds, until garlic gives off its aroma. Add 1/2 cup (125 mL) parsley and season to taste with salt and pepper. Stir in lemon juice and toasted bread cubes. Remove from heat.
Trout: Season trout with salt and pepper; divide stuffing equally and put inside each. Place in a lightly oiled baking dish just large enough to hold the fish in a single layer, and sprinkle wine over top.
Bake at 450°F (230°C) for 5 minutes. Reduce heat to 400°C (200°C) and bake for about 15 minutes, until flesh is opaque and just starting to flake when tested with a fork. Do not overcook. Let stand 3 minutes before serving. Spoon any pan juices over fish and sprinkle remaining chopped parsley over top.
Makes 4 servings.