Thaw and drain the frozen shrimp or crab-flavored fish; set aside. Meanwhile, for crepes, combine all-purpose flour, the 1 cup milk, egg, and salt. Beat until blended. Spray a 6-inch skillet with nonstick spray coating. Preheat skillet; then remove skillet from heat. Pour in 2 tablespoons batter. Lift and tilt skillet to spread batter. Return to heat; brown on one side only. Invert skillet over paper towels; remove crepe. Repeat with remaining batter.
For filling, spray a cold medium saucepan with nonstick spray coating. Heat saucepan over medium heat. Add onion and garlic. Cook until onion is tender, stirring often. Add curry powder; cook and stir for 1 minute more. Then, stir in condensed soup and the 3 tablespoons milk. Remove from heat. Remove 3/4 cup of the soup mixture; cover and chill. If desired, reserve some shrimp for garnish. Stir remaining shrimp or fish and apple into remaining soup mixture.
To assemble, spoon 1/4 cup of the shrimp or fish mixture onto the unbrowned side of each crepe. Roll up. Place filled crepes, seam side down, in a 13x9x2-inch baking dish or 6 individual casseroles. Cover and chill for 2 to 24 hours.
Before serving, stir the reserved soup mixture. Spoon soup mixture on top of filled crepes. Cover and bake in a 350 degree F oven about 30 minutes or until heated through. If desired, garnish with reserved shrimp. Makes 6 servings.