In a medium bowl, mix graham cracker crumbs, powdered sugar, melted unsalted butter, vanilla, salt, and 1 cup creamy peanut butter until smooth and well blended.

Press the mixture evenly into the bottom of a 9x13-inch pan.

Place semisweet chocolate chips and 1/4 cup peanut butter in a microwave-safe bowl. Microwave on high in 15-second bursts, stirring between each, until smooth. Pour the chocolate mixture over the base. If using, sprinkle with chopped peanuts and lightly press so they adhere.

Cover and refrigerate for at least 1 hour before cutting into 15 small bars.