1. Combine first 5 ingredients in a medium shallow dish, stirring well with a whisk. Place bread slices on a flat surface. Spread 2 tablespoons preserves over each of 4 bread slices, and spread 1 1/2 tablespoons peanut butter over each of the remaining 4 bread slices. Assemble sandwiches. Carefully dip 2 sandwiches in milk mixture, turning to coat.
2. Heat a large skillet over medium-high heat. Add 1 1/2 teaspoons canola oil to pan; swirl to coat. Place coated sandwiches in pan; cook 2 minutes on each side or until toasted. Remove sandwiches from pan. Repeat procedure with remaining oil, 2 sandwiches, and milk mixture. Sprinkle powdered sugar evenly over sandwiches; cut each sandwich in half diagonally.