In a medium bowl, combine graham cracker crumbs, powdered sugar, and peanut butter. Mix until well combined and smooth. If using, stir in shredded coconut.
Line an 8x8 inch baking dish with parchment paper, leaving some overhang for easy removal. Press the peanut butter mixture evenly into the bottom of the prepared dish.
In a microwave-safe bowl, melt the chocolate chips and unsalted butter together in 30-second intervals, stirring in between, until smooth and fully melted.
Pour the chocolate mixture over the peanut butter layer and spread it evenly.
Refrigerate the bars for at least 2 hours, or until set. Once firm, lift the bars out of the dish using the parchment paper and cut into squares.