Prepare your muffin tray. If using a silicone tray, no lining is needed as the cups will pop straight out. If using a metal tray, line each hole with a paper cupcake case.
Melt the chocolate in a microwave-safe bowl, heating in 30-second intervals, stirring well between each burst, until completely smooth. Alternatively, melt gently over a bowl of simmering water (bain-marie method). Add coconut oil if needed.
Stir in the peanut butter until the mixture is smooth and fully combined. If the peanut butter is thick, microwave for an additional 20 to 30 seconds to loosen it.
Add the protein crisp cereal and salt (if using). Stir until everything is evenly coated.
Spoon the mixture into the muffin tray and press down firmly with the back of a spoon.
Transfer to the freezer for at least 1 hour, or until fully set. Remove from the tray and allow to sit at room temperature for 5 to 10 minutes before eating for the best texture.
