Peanut Butter, Chicken, & Leek Bites

1 sheet (1/2 pound) frozen puff pastry, thawed in the fridge overnight
1 large leek
1 tablespoon butter
1 tablespoon olive oil
chicken pieces, diced
2 cloves garlic, minced
1 teaspoon soy sauce
1 teaspoon brown sugar
1/4 teaspoon ground ginger
1/4 teaspoon crushed red pepper flakes (more or less to taste)
1/8 teaspoon black pepper
2 tablespoons water
1/3 cup Old Fashioned Smooth peanut butter