To make the chocolate coating: In a large bowl, add the milk chocolate and coconut oil into a heatproof bowl. Using a double boiler, heat until melted. Remove from heat. (Alternatively, microwave in a microwave safe bowl for 30 second intervals, stirring between each interval).
Fill the cupcake liners one-third full with chocolate. Place the tray in the freezer.
To make the filling: In a large mixing bowl, add the melted coconut oil, maple syrup, and peanut butter and whisk together until smooth.
Remove the cupcake pan from the freezer. Spoon the peanut butter filling into the cups and spread to the sides. Place the cupcake pan back in the freezer to set the filling for a few minutes.
Remove the cupcake pan from the freezer and top with the chocolate until full. Top with chopped peanuts and flaky sea salt (optional).
Place back in the freezer to harden, for at least 30 minutes. Transfer to the fridge.