Line a muffin tin with cupcake liners and set aside.
Melt the dark chocolate using a microwave or double boiler until smooth.
Spoon a small amount of melted chocolate into each liner and spread to form the base layer.
Place the muffin tin in the refrigerator for 10 minutes to set.
In a bowl, mix peanut butter, maple syrup, and crispy cereal until well combined.
Spoon the peanut butter mixture evenly over the chocolate base.
Pour the remaining melted chocolate over the peanut butter layer, covering completely.
Sprinkle with sea salt if desired.
Refrigerate for at least 1 hour, or until fully set.
Remove from the liners and enjoy.