Using a handheld or stand mixer fitted with the paddle attachment, beat the butter on medium speed until creamy. Add the peanut butter, vanilla, and salt, and beat until smooth and combined.

Add the icing sugar, and beat on low until combined. Fold in the crispy rice cereal. The mixture will be crumbly, but you should be able to roll into balls.

Roll the dough mixture into 1-inch balls (about 0.5oz each), and place on a baking tray lined with parchment paper or a silicone mat. You should have about 40 - 45 balls.

Refrigerate until firm - about 1 hour.

Add the chocolate to a microwave-safe bowl, and heat in 20 second intervals, stirring after each one, until melted and smooth. Leave to cool for 5 minutes.

Dip each peanut butter ball into the melted chocolate, and place back onto the baking tray. Allow to set in the fridge before serving.