Line a 12 cup muffin tin with paper liners. Set aside.
Melt the butter in a small saucepan over medium heat. Stir in the peanut butter, graham cracker crumbs, and maple sugar and mix well. Remove the mixture from the heat. Evenly divide the mixture, approximately 2 Tbsp per cup, among the muffin cups.
Combine the cacao nibs and nut milk in another pan. Stir over medium heat until the cacao nibs have melted. Spoon the chocolate evenly over the peanut butter mixture. Top with chopped nuts. Place in refrigerator for 1 1/2 hours before serving.