Spread mustard evenly over 1 side of each bread slice. Layer each of 4 bread slices, mustard sides up, with 2 oz. ham and 1 cheese slice. Top with remaining bread slices, mustard sides down.
Whisk together egg substitute and milk in a shallow dish. Dip both sides of each sandwich into egg mixture.
Cook, in batches, in a large nonstick skillet coated with cooking spray over medium heat 3 minutes on each side or until lightly browned. Top each with 1 Tbsp. chutney, and, if desired, dust with powdered sugar.