Place pork between 2 sheets of heavy-duty plastic wrap; pound each piece to a 1/4-inch thickness, using a meat mallet or rolling pin.
Combine mustard and next 3 ingredients in a small bowl. Place pork in a shallow dish; spoon 2 tablespoons mustard mixture over pork, turning to coat. Let stand 15 minutes.
Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add pork, and cook 4 minutes on 1 side; turn pork, and spoon reserved mustard mixture over pork. Cook pork 2 minutes or just until done.
Add water, stirring slightly; cook 2 minutes or until slightly thickened. Turn pork to coat, and place on a serving platter. Pour pan juices over pork.